Download LEUKEMIA is a cancer in blood

LEUKEMIA is a cancer in blood-forming cells.
LYMPHOMA is a tumor developing in lymphatic tissues.
CARCINOMA is a tumor developing in any part of the epithelium.
MELANOMA is a tumor developing in the pigment of the skin.
SARCOMA is a tumor developing in muscles and connective tissues.
CHARACTERISTICS OF CANCER CELLS
1. LACK DIFFERENTIATION
cancer cells do not differentiate and do not contribute to the function of the body.
2. ABNORMAL NUCLEI
They have large or multiple nuclei with mutated chromosomes.
3. FORM TUMORS
Cancer cells grow and divide rapidly until they accumulate and form a lump of cancer
cells called a tumor. A BENIGN tumor is an accumulation of non-cancerous cells
because they stay in their own capsule (encapsulated) and do not invade.
MALIGNANT tumors are cancerous cells that spread and invade.
4. INDUCE BLOOD VESSEL FORMATION
Since these tumors need nutrients, they create new blood vessels just for them to feed on.
5. METASTASIZE
Pieces of the tumor break off and travel in the bloodstream to any new location,
invade nearby tissues and continue their massive cell division and growth there. If
there is a tumor in the lung, it is biopsied (the doctor surgically takes out a piece). If the
cells are lung cells, it is lung cancer. But if the cells are pancreas cells, it is pancreatic
cancer that has metastasized.
ORIGIN
There are many factors that play a role in the development of cancer, including
heredity factors, carcinogens, and mutagens.
CARCINOGEN is an environmental agent that contributes to cancer
Examples of a carcinogen are radiation, toxic chemicals, and viruses.
MUTAGEN is an agent that increases chances of DNA change or mutation.
PAP SMEARS detect cervical cancers. They just swab the cervix and look at the
cells under a microscope.
MAMMOGRAMS are diagnostic procedures to detect breast cancer. The breast is
just placed on a special type of machine like an x-ray.
COLONOSCOPY is a diagnostic procedure to detect colon cancer. A scope is
inserted into the rectum so the doctor can look for polyps.
The American Cancer Society says the following are signs of cancer:
Change in bowel or bladder habits
A sore that does not heal
Unusual bleeding or discharge
Thickening or lump in breast or elsewhere
Indigestion or difficulty swallowing
Obvious change in wart or mole
Nagging cough or hoarseness
PREVENTION
1. BEHAVIORS
DON’T smoke, sunbathe, drink alcohol, or get too many x-rays. Smoking cigarettes is
associated with many types of cancers, including cancer of the lung, larynx, throat,
and urinary bladder.
DO be tested (self-breast exams and Dr. check-ups), be aware of chemical hazards at
work, and be aware that using estrogen for menopause symptoms must be combined with
estrogen, otherwise there is an increased risk of cancer. The American Cancer Society
recommends breast self-exams and testicular self-exams every month.
2. DIET
Avoid fats, salty, smoke-cured, pork, and pickled foods. Eat plenty of fiber, green leafy
vegetables and fruits, and eat cabbage, broccoli, Brussels sprouts, and cauliflower. There
are things you can change in your diet that help prevent cancer. Green leafy
vegetables such as cabbage and broccoli are associated with cancer prevention, as
are vitamins A and C.
PREVENTION OF SKIN CANCER:
A. use broad-spectrum sunscreen
B. stay out of the sun altogether from 10-3
C. wear protective clothing
D. wear sunglasses
E. do not use tanning machines
TREATMENT OF CANCER
1. RADIATION
When someone has surgery to remove a tumor, it is often followed by radiation
because the cancer cells may have spread throughout the body.
REPRODUCTION
A. BODY of the penis is the exposed region
B. GLANS is the tip of the penis.
Surrounding the glans is the PREPUCE (foreskin), a continuation of the skin of the
penis that extends over the glans.
Viagra is a medicine which allows vasodilatation (to encourage a penile erection),
but if you have heart disease, it can give you a heart attack. Viagra can also cause
vision problems.
An erection squeezes the veins shut so the blood can’t leak out. If Viagra (or anything
else) causes an erection for longer than four hours, the erection decreases the blood
flow, and the tissue is killed.
2. SCROTUM
A. TESTICLES makes sperm.
B. VAS DEFERENS is the tube that the sperm goes into.
C. PROSTATE GLAND is where the vas deferens passes through.
D. SEMINAL FLUID is the liquid that carries the sperm. It is made by the
prostate gland.
E. SEMEN is the seminal fluid plus the sperm. The semen is then dumped
into the urethra during ejaculation. The urethra is the same tube that excretes urine.
In order for sperm to be produced, the temperature has to be a few degrees lower than
normal (35˚C or 94˚F instead of 37˚C or 98˚F). To insure a lower temperature, the
testes are located outside of the body, in the scrotum (outside of the pelvis). The
temperature is maintained by muscles that elevate and depress the testes.
PROBLEMS
There is an opening in the groin area called the INGUINAL CANAL. If you do heavy
lifting, it increases the abdominal pressure, and intestine gets pushed into it =
INGUINAL HERNIA (surgery).
VASECTOMY is the #1 birth control method in the US.
Infertility
The most frequent cause of infertility in males is low sperm count and/or abnormal
sperm. Disease, radiation, chemicals, high testes temperature, and drug abuse can
also contribute to this condition.
PROSTATE
PROSTATIC HYPERTROPHY (enlarged prostate). It can constrict the urethra,
making it hard to urinate.
FEMALE REPRODUCTIVE SYSTEM
Consists of the following:
1. Ovaries
2. Fallopian Tubes
3. Uterus
4. Vagina
5. External genetalia
The two hormones that influence the development of female secondary sex
characteristics are estrogen and progesterone.
The average ovarian cycle is 28 days.
Day 14 OVULATION. Can be some cramping.
Day 28
Menstruation starts as the uterine lining breaks down  Day 1
A woman is only fertile when the egg is released, but there is an OVARIAN REFLEX
which is ovulation in response to sex (not necessarily with orgasm). In addition, sperm
live for 7-10 days. That means that you can have sex during menstruation, and the
sperm might live inside past ovulation. There is no safe time to have unprotected sex.
Unprotected sex once a week = 90% chance of pregnancy.
Infertility
One of the most common causes of infertility in women is STD (sexually transmitted
disease). We’ll talk about that later. Also, Fat is needed to have the menstrual cycle.
Skinny and athletic women may not menstruate.
Women who have trouble conceiving take fertility pills, which causes 100 eggs to
develop, 4-5 of which may mature  multiple births. Therefore, fertility pills frequently
result in multiple births.
Birth Control Pills are made of estrogen, so they inhibit the development of the eggs, but
the uterine lining still grows. You take them for 3 weeks, and then take one week off to
allow for menstruation. They are 99% effective if taken properly. You have to be careful
to take the pill not only every day, but at the same time every day, to keep from
getting pregnant. Some of the new estrogen pills can cause a period only every 3 months
instead, but there are side effects. Stop BCP 6-12 months before planning conception, or
there may be birth defects.
Implantable birth control = NORPLANT, etc (capsules of estrogen surgically implanted
under the skin of the arm), releases tiny amount of estrogen continually.
Condoms are also 99% effective if used correctly; if not, only 85% effective. Solution =
put the woman in charge of the condom, and the failure rate drops dramatically.
2. FALLOPIAN TUBES
When the egg is released, it goes into the fallopian tube. .
ECTOPIC PREGNANCIES
The egg is normally fertilized in the fallopian tube, goes down into the uterus and
implants there. If it implants in the fallopian tube = ECTOPIC PREGNANCY. This
is fatal to the mother and embryo, but nowadays there are few deaths of the mother
because it is very painful, so she will go to the ER and they will do surgery. A woman
who goes into the ER with abdominal pain will always get a pregnancy test.
Sperm swim out of the opening of the fallopian tube and into the body cavity.
That means any STD can also enter there, causing PELVIC INFLAMMATORY
DISEASE (PID), where it spreads to all organs in the pelvis. This STD is chronically
extremely painful for the rest of the woman’s life, and there is no cure and no treatment.
The most common cause of infertility in women is STD. The inflammation and
scarring closes off the fallopian tube.
TUBAL LIGATION is a method of birth control where a piece of the fallopian tube is
cut out, and there’s no way for the sperm to reach the egg. It is more complicated than a
vasectomy, so it is done less often than a vasectomy.
3. UTERUS
The uterus consists of a BODY, CERVIX, and VAGINA. The cervix is the neck of the
uterus.
When a woman stands upright, the uterus sits on top of the urinary bladder.
PROBLEMS WITH THE UTERUS
ENDOMETRIOSIS is a very strange condition. Pieces of the uterus wall
(endometrium) are supposed to fall down the vagina during menstruation, but sometimes
its cells go up the fallopian tube and enter the body cavity. They can lodge anywhere;
on top of the lung, kidney, etc. These cells still respond to hormone changes, grow, and
break down and die, causing a lot of weird pain during menstruation. It’s difficult to
diagnose because the pain goes away before the doctor appointment. The symptoms
vary, depending on the location. One lady had it on her lung and got a collapsed lung
every month. Treatment is to give hormones to prevent menses.
FIBROIDS
These are benign tumors like scar tissue. They can get large and be painful, especially
during contraction of menses and pregnancy. Fibroids are the most common reason for
hysterectomy (surgical removal of the uterus).
HYSTERECTOMY comes from the Greek “hysteria”. It was thought that only women
get hysterical because they have a uterus. Now we know that’s not true. They get
hysterical because they have ovaries! The surgery involves going through the abdominal
wall, cut the fallopian tubes, and yank the uterus out through the vagina.
4. VAGINA: At the vaginal opening the skin extends into the opening = HYMEN. It is
thin and rubs away during first sexual intercourse.
5. EXTERNAL GENITALIA = VULVA
Parts of the vulva
A. LABIA MAJORA are thick folds of tissue around the labia minora. It is
the female equivalent of the scrotum.
B. CLITORIS (equivalent of the penis), which also has erectile tissue
During childbirth the vaginal opening enlarges, so it will either stretch or tear. If it tears
all the way back to the anus, it will get badly infected. The surgeon can do a controlled
cut on the vagina to enlarge the birth canal = EPISIOTOMY. Local anesthesia is
given first.
BIRTH CONTROL METHODS
(Magic trick: the magic coloring book)
This is a list of some contraceptives in order of effectiveness
Abstinence
Vasectomy
Tubal ligation
Birth Control pills
Intrauterine device (IUD)
Diaphragm
Condom
Jellies, creams, foams
Rhythm Method
Penis withdrawn before ejaculation
The most reliable method of birth control is abstinence, that is, the absence of sexual
intercourse. This form of birth control has the added advantage of preventing
transmission of a sexually transmitted disease.
Oral contraception (birth-control pills)
Involves taking a combination of estrogen and progesterone for 21 days a month.
They prevent ovulation. There can be some serious side effects: increased risk of heart attack.
Intrauterine device (IUD)
This is a small piece of mold plastic that is inserted into the uterus by a physician. It
prevents implantation. Problem is that it can harbor bacteria and become infected.
Diaphragm
This is a soft latex cup with a flexible rim that fits over the cervix and can be inserted into
the vagina two hours at most before sexual relations. It must be used with spermicide.
Jelly or cream and should be left in place at least six hours after sexual relations.
Problem is that it takes some skill to use; must be exactly in the proper position.
Condom
A condom, when used in conjunction with a spermicide, the protection is better than with
the condom alone. It also protects against sexually transmitted diseases. Problems occur
unless air must be squeezed out of the tip after it is in place or it will break. Use of
hand creams will also cause it to break. Only K-Y Jelly (water-based lubricant) is safe
to use near a condom.
The least effective method is withdrawing the penis before ejaculation. Statistics say
that there is a 30% chance of pregnancy.
Is possible for a baby to have five parents:
(1) sperm donor, (2) egg donor, (3) surrogate mother, and (4) and (5) adoptive mother
and father.
SEXUALLY TRANSMITTED DISEASES (STDS)
1. VIRUSES
A) HIV / AIDS (acquired immunodeficiency syndrome): Caused by a virus that infects white
blood cells.
Prevalence
JOKE: Did you know senior citizens are the leading carriers of AIDS? Yup…hearing
aids, nursing aids, walking aids, Band-Aids!
Seriously, About 40 million people worldwide have become infected with HIV, and of
these, 12 million have died of AIDS. A new HIV infection occurs every 15 seconds, the
majority in heterosexuals. Most infected people live in Africa (66%) where it is believed
HIV infections first began, but new infections are now occurring at the fastest rate in
Southeast Asia and India.
In the United States, HTV infections are more prevalent among African Americans and
Hispanics. Everyone who is sexually active or who use IV drugs are at risk.
Symptoms of an HIV Infection
It attacks white blood cells to destroy a person’s immune system. During the initial
phase, there are no symptoms and the blood test is negative, yet the person is highly
infectious.
Several months to several years after infection, symptoms begin with swollen lymph
nodes, severe fatigue, fever with night sweats, and diarrhea are present. If the virus enters
the brain there will be loss of memory, inability to think clearly, loss of judgment, and/or
depression.
Persons with AIDS die from opportunistic diseases, not from the HIV infection
itself. An opportunistic infection is when a bacteria that frequently lives on our body
without causing disease but will cause disease if given the opportunity. One opportunity
that can present itself is when the immune system is weakened.
Treatment
There is no cure for AIDS, but they can be given therapy that usually consists of two
drugs that prevent mutation of the virus to a resistant strain. Unfortunately, if the virus is
the resistant strain, there is no drug therapy.
Transmission of HIV
The largest group of people with AIDS in the United States is homosexual men, but the
largest population of new cases are intravenous drug users and heterosexuals.
Women now account for 20% of all newly diagnosed cases of AIDS. An infected
woman can pass HIV to her unborn children or to a newborn through milk.
Transmission at birth can be prevented if she takes AZT, and delivers by C section.
HIV is spread in body fluids, such as blood, from one person to another. (Blood
transfusions are now tested for the presence of HIV, so risk of contracting an
infection in this manner is now considered very unlikely).
B) Herpes Infections
The herpes viruses cause various illnesses. Chicken pox and mononucleosis (EpsteinBarr) are examples of a herpes virus. However, only the herpes simplex virus is
sexually transmitted. They infect mucosal linings such as the mouth and vagina. There
are two types of herpes simplex viruses: type 1 usually causes cold sores and fever
blisters, while type 2 more often causes genital herpes. However, oral sex with someone
with a fever blister can cause genital herpes and oral sex with someone with genital
herpes can cause fever blisters.
Cold Sores and Fever Blisters
Cold sores are usually contracted during childhood from a smooch from a well-meaning
adult with a cold sore. The sores heal and break out again during times of stress
throughout the person’s life. The stress can be from emotional stress, illness, menstruation, high fever, colds, or exposure to sunlight. These sores are infectious for at
least three to four days until the sores begin to heal. Contact with the sores or any
contaminated object can cause the virus to be transmitted.
Genital Herpes
Genital herpes is what causes genital warts.
All warts are caused from a virus. A regular wart on the hands or plantar wart on the
feet is harmless, but they can spread, get bigger, and cause discomfort. Genital herpes is a
sexually transmitted wart. Over one million persons a year become infected, but not
everyone goes in for treatment. It is caused from having intercourse with someone who
has genital herpes, or from having oral sex with someone with a cold sore.
Transmission and Symptoms
In some people there are no symptoms, so many people don’t know they have them.
They start as a tingling or itching sensation before blisters appear on the genitals. Once
the blisters rupture, they leave painful ulcers that may take as long as three weeks or as
little as five days to heal. The blisters may be accompanied by fever, some burning on
urination, swollen lymph nodes in the groin, and in women, a copious vaginal discharge.
As with cold sores, the blisters come back from the same stress situations.
A newborn can become infected by passage through the birth canal so they have to
be delivered by C-section.
Genital warts are associated with cancer of the genitals. Teenagers with multiple sex
partners are very susceptible to genital warts, and more cases of cancer of the cervix are
being seen among this age group.
Treatment
There is no cure for genital herpes. There are some medicines in the form of pills or
ointment that disrupt the reproduction of the virus and so relieve the initial symptoms at
the first sign of outbreak, but it will always come back later. They can be temporarily
removed by surgery, freezing, acid, or laser. However, as with all warts, there is a high
likelihood of reoccurrence. Even after treatment, the virus can be transmitted because
the wart may look gone, but it lingers in the subdermal tissues. Therefore, abstinence or
use of a condom is necessary.
C) Hepatitis Infections
There are several types of hepatitis. There is no treatment and no cure, but there is a
vaccine.
Hepatitis A
This is a virus you get when you or a food worker doesn’t wash the hands after going
to the bathroom, and then you eat. It can also be sexually transmitted through
oral/anal contact.
Hepatitis B
This is the form that is primarily spread by sexual contact or sharing needles by
drug users.
Only about 50% of infected persons have flu-like symptoms, including fatigue, fever,
headache, nausea, vomiting, muscle aches, and dull pain in the upper right of the abdomen. Jaundice, a yellowish cast to the skin, can also be present. Some persons have an
acute infection that lasts only three to four weeks. Others have a chronic form of the
disease that leads to liver failure and a need for a liver transplant.
Hepatitis C
This is the form you get from infected blood. It is very serious and can lead to
chronic hepatitis, liver cancer, and death.
Since there is no treatment for an HBV infection, prevention is imperative by a vaccine, which is safe and does not have any major side effects. This vaccine is now on the
list of recommended immunizations for children.
2. BACTERIA
Bacterial diseases are controlled by preventing transmission and by antibiotics.
Abstinence or monogamous relations (always the same partner) with someone who is free
of an STD will prevent transmission. Otherwise, the use of a condom and avoidance of
oral/genital contact is recommended.
A) Chlamydia
Chlamydia is the leading STD in the United States. There are about 6 million new
cases per year. Five times more women than men go in for treatment for this because
women have more symptoms and men who are infected don’t know it.
Symptoms
At first there may be no symptoms, but after 1-3 weeks there may be a mild burning
sensation on urination and a mucous discharge in vagina. Unfortunately a physician
mistakenly may diagnose it as a urinary tract infection and prescribe the wrong type of
antibiotic; until they realize the medicine is not working, the person is still contagious.
If the infection spreads to the ovaries, she’ll get pelvic inflammatory disease (PID)
results. This is a very painful condition with no treatment and no cure. It also causes
sterility. The woman has to live with this severe pain for the rest of her life.
If a newborn comes through the birth canal of a women with Chlamydia, its eyes
become infected and results in blindness. This is the leading cause of blindness in
third-world countries. That is sad, because all it requires are some eye drops in the
infant right after birth, and it will prevent this. This STD is easily cured with tetracycline.
B) Gonorrhea
Gonorrhea was at an all-time high in 1978, but it’s going down now. Women using birthcontrol pills or an IUD have a greater risk because they cause the genital tract to be more
receptive to pathogens.
Symptoms
Unlike Chlamydia, gonorrhea symptoms are more obvious in men than in women. Men
have pain on urination and a milky urethral discharge three to five days after contact.
In women, there are usually no symptoms until after it spreads to the ovaries, again
causing PID (a million women a year get this). Since PID scars up the area around the
ovaries, pregnancy can result in an ectopic pregnancies.
The leading cause of blindness in newborns is from Chlamydia infections in their
eyes after passing through an infected birth canal. Adults can get it in their eyes, too,
if they touch an infected area and rub their eyes. Eye infections cause blindness.
Oral/genital contact can cause infection of the mouth, throat, and the tonsils. Gonorrhea
can spread to internal parts of the body, causing heart damage or arthritis.
Transmission and Treatment
The chances of getting a gonorrheal infection are good. Women have 50—60% risk,
while men have a 20% risk of contracting the disease after even a single exposure to an
infected partner. Painful urination usually indicates gonorrhea. It is easily cured
using antibiotics.
C) Syphilis
Syphilis is caused by a bacterium that has a tail and can move, so it is particularly nasty.
Syphilis has three stages.
1) Primary stage: an ulcerated sore with hard edges appears at the site of infection.
The ulcer heals itself, but it is just gearing up for the next stage.
2) Secondary stage: the bacteria spread throughout the body and a rash forms all
over, although it is not itchy. Again, it heals itself, but the worst is on its way.
3) Tertiary stage: lasts until the patient dies. It weakens the arteries, causing
aneurysms, and is known for attacking the brain. Symptoms include mental
impairment, blindness, and insanity. Henry VIII died from syphilis.
Diagnosis and Treatment
Diagnosis of syphilis can be made by blood tests and microscopic examination of fluids from
lesions. It is easily cured by penicillin, but once it enters the last stage, there is no cure
and is fatal.
3. Other Organisms that cause Sexually Transmitted Diseases
A) Trichomonas is a single cell parasite which is transmitted sexually and causes
severe itchiness a woman’s vagina. Men are usually asymptomatic (no symptoms).
B) Fungi and Yeast are pathogens from the plant kingdom. When a woman takes an
antibiotic while using birth-control pills, it disrupts the normal balance of bacteria,
and allow normal yeast there to cause an infection.
C) Lice are insects that can infect the hair of humans. Head lice is well known for
infecting the hair of schoolchildren; lice on the pubic hair are called “crabs”, and are
sexually transmitted and also can be contracted by contact with an infected person’s
clothing or bedding. They suck blood from their host and cause severe itching,
particularly at night. The pubic hair, underarm hair, and even the eyebrows can be
infected, and it can be self-diagnosed by examination of the hair. Protozoa, yeast,
worms, and lice are all easily treated with antibiotics and disinfection of sheets and
clothing.
Prevention is still the best way to manage STDs.
1. The use of a condom along with a spermicide that contains nonoxynol-9
2. The avoidance of oral/genital contact
3. Have a monogamous relationship
4. Don’t have sex with someone who has a STDs
5. Don’t have sex with an intravenous drug user.
REPRODUCTIVE
Why do men have nipples? 61
Can you get pregnant while you are having your period? 84
Do oysters really make you horny? 84
Does the kind of underpants men wear affect their fertility? 93
Can hot tubs make you infertile? 96
Can a man ever run out of sperm? 97
Will yogurt cure a yeast infection if you put it "inside"? 104
Is there such a thing as male menopause? 210
EMBRYONIC DEVELOPMENT
This is an amazing process that one cell can grow into an entire organism is 9 months!
FERTILIZATION
SPERM
This is the simplest and smallest cell in the body. It consists of a FLAGELLUM (to
swim), a NUCLEUS (to carry DNA), and an ACROSOME (for fertilization.
The function of the sperm is to allow the nucleus to reach the egg.
The
relative sizes of the egg to the sperm
IDENTICAL TWINS is when one fertilized egg develops into two masses. These have
the same embryo, same genetic make-up. Occurs randomly. If more than one egg
becomes fertilized = FRATERNAL TWINS.
If the identical twins don’t completely separate = CO JOINED TWINS, which are
always identical. They can be joined anywhere. Sometimes they are joined at the chest
and share a heart, or are joined at the head and share meninges and a blood supply. This
can be detected in utero by ultrasound.
The first known co joined twins were from Siam, so they were called Siamese twins.
These two brothers had two heads but one pair of legs. They married two different
women and had lots of kids. One died two days before the other one.
EGG
The egg has to support the embryo for a few weeks. Eggs are so large they can be seen
with the naked eye. It contains a membrane filled with nutrients = YOLK SAC
When the sperm reach the egg, millions of them break open their acrosome and
release enzymes to digest the outer layer of the egg to get in. The first sperm to do this
causes the egg to prevent any other sperm from getting in. It is impossible for more than
one sperm to fertilize one egg. Fertilization occurs in the fallopian tube or the uterus.
The fertilized egg travels down to the uterus where it should implant in the wall. If there
is no implantation, menses (shedding of the uterus lining) occurs.
The egg begins rapid cell division. This occurs as the egg is going from the fallopian tube
to the uterus. It takes one week to get to the uterus.
DAY 1: The fertilized egg is called a ZYGOTE. It is only one cell.
DAY 7: The egg is thousands of cells = BLASTOCYST, which begins to implant into
the uterus by burrowing into it like a parasite.
Fertilization occurs on about day 14 of the menstrual cycle.
Implantation occurs on about day 21 of the menstrual cycle.
The blastocyst secretes a hormone which is measured in a pregnancy test. It will be in
sufficient quantities to be measured within about one week after a missed period.
First and Second Months
Embryonic development takes place up to 2 months; after that it starts to look human, and
is called a fetus. All that’s left is growth and differentiation. The first thing to develop
is the nervous system; it starts developing in the third week! By the end of the
second month, all the major organ development is done, except for such things as the
lungs and liver which mature later.
Third and Fourth Months
Eyelashes, eyebrows, hair on the head, and fingernails appear. Development of genitals
begins at eight weeks. Both the male and female look identical at first. Females stay the
same, and males have fetal testosterone which causes a change. By the third to fourth
month it is possible to distinguish males from females. By the end of the fourth
month, the fetus is 6” in length and weighs 6 oz. OVERHEAD
Fifth through Seventh Months
The mother begins to feel fetal movement. The fetal heartbeat is loud enough to be
heard when a physician applies a stethoscope to the mother’s abdomen.
During these months, the eyelids open fully. At the end of this period, the fetus is 12”
and weighs 3 lb. It is possible that if born now, the baby will survive. OVERHEADS
Eighth and Ninth Months OVERHEADS
As the end of development approaches, the fetus usually rotates so that the head is
pointed toward the cervix. However, if the fetus does not turn, then the likelihood of a
BREECH BIRTH (rump first) may prescribe a cesarean section. At the end of nine
months, the fetus is about 20” long and weighs about 7 lb. OVERHEAD
PLACENTA
This allows oxygen and nutrients to diffuse from the mother to the fetus, and waste
products to diffuse from the fetus to the mother. The
UMBILICAL CORD connects the placenta to the fetus. The purpose of the placenta
is to make sure there is enough O2 and nutrients for the fetus. Other things can diffuse
across the placenta, including drugs, viruses, alcohol, and tobacco products.
Another thing that can cross the placenta are vitamins. There are new studies that
prenatal vitamins are causing vitamin toxicity in the fetus, resulting in brain dysfunction.
It’s better to just eat right or take just a regular multivitamin at the most.
What determines if you have an "innie" or "outie" belly button?
Only about 10% of the population has "outies." whether you end up with an innie or an outie is
hereditary.
AMNION
This is the sac filled with fluid that the embryo sits in. The function of the fluid is:
1. Cushions embryo
2. Allows the embryo to float so it can develop in three dimensions
3. Allows room for the embryo/fetus to move
The amnion ruptures just before birth = WATER BREAKING.
Sometimes it doesn’t tear, so the doctor goes in with a crochet hook device to puncture it.
In the fluid are fetal skin cells which can be gathered by an AMNIOCENTESIS. This is
only helpful in identifying chromosomal problems, not birth defects.
CHILDBIRTH
As the uterus contracts, the cervix dilates. In a normal birth, the baby is born head
first, then the placenta separates and is delivered about 45 minutes later; this is
called the AFTERBIRTH. The mother will lose about 1 liter of blood, but she has 2
extra liters now anyway.
CESAREAN is an incision through the abdominal wall to deliver the baby that way. She
can give birth vaginally next time. Most C-sections are unnecessary, but the doctor
doesn’t know which ones are unnecessary.
There are many FADS in birthing children. The doctor doesn’t need to be in the room,
but one should be next door. Water births are a dumb idea because humans do not
naturally give birth under water, and we are air-breathing creatures. Also, the mother
usually defecates as the baby is being born, and the baby will be exposed to the feces in
the water. There is also some blood lose during delivery, and a small amount of blood
will color the water just as red as a large amount of blood, so there is no way to measure
if there is excess blood loss.
FETAL CIRCULATION
By three weeks:
Nervous system is forming
Heart begins to form
GI system starts to form.
How long has it been since the mother missed her period? Just one week.
The nervous system and cardiovascular system has already started developing.
Therefore, it’s too late to stop drinking and smoking AFTER you find out you’re
pregnant!
PROBLEMS WITH DEVELOPMENT
SPONTANEOUS ABORTION (Miscarriage)
Can occur for many reasons. No one knows the rate of miscarriages, but they guess that
70% of fertilized eggs get miscarried, and about 30% of implanted eggs miscarry.
As the fetus grows, sometime part of the spinal cord doesn’t close; this is SPINA
BIFIDA. The baby can be paralyzed from the waist down.
CLEFT LIP or CLEFT PALATE is seen in 1/700 births. The oral cavity is open to
the nasal cavity. It is associated with alcoholism; its incidence goes up to 1/200 in
alcoholics.
FETAL ALCOHOL SYNDROME is when the fetus has become damaged from the
mother drinking alcohol during pregnancy. Sometimes just one day of drinking (if it’s
at a significant point in the development) will cause this. The child will have mental
retardation and the eyes are slightly wider apart.
PROBLEMS WITH MALE DEVELOPMENT
LACK OF TESTOSTERONE
Without fetal testosterone, the male child has female genitals. Then at puberty, the adult
testosterone kicks in, and they become normal men. There is a village in the Dominican
Republic that has this occur fairly often. They call it pinte waves (“balls at 15”).
The Olympics use genetic tests to make sure the females are really females.
The pills for men that prevent baldness block testosterone. A pregnant mother is not
allowed to even touch these pills, or it will absorb through her skin and cause
developmental problems in the child’s genitals.
Development of a baby does not end at birth.
The digestive system develops for 1 year after birth. The intestine can absorb (not digest)
whole proteins for one year.
Breast milk has antibodies from the mother, so as long as the baby is breast feeding
(up to one year), the baby is immune to all the infectious diseases that the mother is
immune to. Breast feeding longer than one year will no longer be providing any
antibodies to the baby.
Puberty in girls begins inwardly around 9 years old, and boys start at 11, but the outward
signs don’t show for a couple years.
The skeletal system develops until 14-18 years, except the pelvic bones in girls don’t
finish growing until age 25; that’s why it’s better to wait until then before giving
birth.
Parts of the nervous system and brain do not even start to develop until age 16.
Development continues through puberty. After that, a person is considered physically
mature.
PREVENTING BIRTH DEFECTS
At least 1 in 16 newborns has a birth defect, either minor or serious.
Only 20% are due to heredity. That means 80% of birth defects can be prevented.
Proper nutrition is a must, especially needed is enough folic acid.
X-rays must be avoided since they cause mutations and leukemia.
Toxic chemicals, such as pesticides also cause mutations.
Cigarette smoke not only contains carbon monoxide but also other toxic chemicals.
Babies horn to smokers are often underweight and subject to convulsions.
Pregnant Rh negative women should receive an Rh immunoglobulin injection to
prevent the production of Rh antibodies. These antibodies can cause nervous system and
heart defects. This is only a concern if the baby is Rh positive.
Sometimes, birth defects are caused by disease-causing organisms.
Females can be immunized before the childbearing years for rubella (German measles),
which in particular causes birth defects such as deafness.
The AIDS virus in a pregnant woman causes the baby to have AIDS and mental
retardation. When a mother has herpes, gonorrhea, or Chlamydia, which are STD’s that
infect the vagina, newborns can become infected as they pass through the birth canal, but
they can be delivered by cesarean section.
Pregnant women should not take any type of drug except prescribed by a doctor.
Certainly, illegal drugs, such as marijuana, cocaine should be completely avoided.
“Cocaine babies” now makeup 60% of drug-affected babies. Cocaine babies have visual
problems, lack coordination, and are mentally retarded.
The drugs aspirin, caffeine (present in coffee, tea, and cola), and alcohol should be
severely limited. Babies born to women who drink while pregnant are apt to have fetal
alcohol syndrome (FAS). These babies have decreased weight, height, and head size,
with malformation of the head and face, and have mental retardation.
Sex hormones, including birth-control pills, can cause abnormalities of the sex organs.
The morning sickness pill called thalidomide is well known for having caused
deformities of the arms and legs in children born to women who took the drug. Of course,
this medicine was taken off the market when they realized this, but sometimes you still
see these kids who have grown up; I’ve seen a lot from Mexico.
GENETICS: MITOSIS
Mary was a very attractive young woman who liked to play ice hockey. Her high school gym
teacher took an interest in her ability and gave her extra coaching. She hoped that one day Mary
would play on an Olympic team. But something was wrong. Mary was sixteen and still not
menstruating. Her parents decided to have her undergo a series of medical tests. Much to the
surprise of everyone, Mary had an X and Y chromosome in the nucleus of her cells. She was a
chromosomal male.
The doctor explained to Mary and her parents that Mary had testicular feminization syndrome.
She has internal testes that produce testosterone but her cells won’t respond to it. Her genitals are
like those of a female and she has well-developed breasts. However, she will never be able to
have children. Mary will be able to go on and play hockey in the Olympics but she has to always
carry a letter explaining her condition. Otherwise she will be disqualified because of her sex
chromosomes.
This is an example of various syndromes that occur when people have chromosomal
abnormalities.
Chromosomal Inheritance
In the nucleus of a cell there are chromosomes, arranged in pairs which are joined in the
center. Each of these pairs are called a called a karyotype ( type of chromosome pair).
Humans have 23 pairs of chromosomes. When they are taken out of a cell for genetic
testing, scientists arrange the pairs in order of their assigned name (which is a
number from 1-23). This procedure is called karyotyping.
Males have one pair of chromosomes that are not the same length. The larger
chromosome in this pair is the X chromosome and the smaller is the Y chromosome.
Females have two X chromosomes. This pair is called the sex chromosomes because they
contain the genes that determine the sex. Therefore, males are called XY and females
are called XX.
GENES are made of DNA and control the characteristics of the individual.
Genes are like small dots on each chromosome. Each dot contains the blueprint for some
aspect of the body. One gene is for eye color, one for liver function, one for right or left
handedness, etc. Every aspect of the body corresponds to a gene on one of the
chromosomes.
Human Cell Division
All cells in our body divide by a process called mitosis, which ensures that each and
every cell has a complete number of chromosomes. Mitosis produces two daughter
cells with the same number and kind of chromosomes as the parent cell.
Here’s a TQ: If a parent cell has 7 chromosomes prior to mitosis, how many
chromosomes will the daughter cells have? Answer = 7.
In addition to mitosis, the sex cells (and only the sex cells) undergo a second process call
meiosis, in which each daughter cell has only half of the chromosomes. In males, it
produces the cells that become sperm; in females, it produces the cells that become eggs.
The sperm and the egg are the sex cells, or gametes. GAMETES contain half the number
of chromosomes compared to the rest of the body cells.
Therefore, meiosis requires two nuclear divisions, resulting in four daughter cells,
each with half of the parent chromosomal number
When a sperm cell fertilizes an egg, the resulting zygote has the all of the chromosomes
from each of the sex cells, for a total of 46 (or 23 pairs). Thereafter, when the cells of the
zygote/embryo/fetus/infant/child/adult divide by mitosis, each cell has 23 pairs of
chromosomes.
MITOSIS
Mitosis is cell division that produces two daughter cells, each with the same number and
kinds of chromosomes as the parent cell (the cell that divides). Therefore, following
mitotic cell division, the parent cell and the daughter cells are genetically identical.
Stages of Mitosis
The process is divided into four phases: prophase, metaphase, anaphase, and telophase.
You need to know the order of these phases.
Prophase
The nuclear envelope dissolves away, and the chromosomes are released into the
cytoplasm of the cell. The chromosome pairs start to shorten and thicken as they get
ready to make a clone of themselves.
Metaphase
During metaphase, the chromosomes line up at the center of the cell, and they make a
copy of themselves. Now there are 4 chromosomes #1, 4 chromosomes #2, and 4 of all
the other chromosomes (instead of 2 of each). That means there are 46 pairs of
chromosomes lined up in the center of the cell.
Anaphase
At the start of anaphase, the sister chromosomes separate and move toward opposite
sides of the cell. There will now be 23 pairs of chromosomes on each side of the cell.
Telopbase
Telophase begins when the chromosomes arrive at the poles. A nuclear envelop now
forms around each set of chromosomes, so at this phase, the parent cell has two nuclei,
each with a complete set of chromosomes. Telophase is characterized by the formation
of two daughter nuclei. At the very end of telophase, the cell membrane pinches in two
so that there are two new cells.
MEIOSIS
Meiosis only occurs in the testes and ovaries when they are ready to make an egg cell or a
sperm cell. Meiosis occurs right after mitosis, so it requires two additional cell divisions
and results in four daughter cells, each having half the number of chromosomes as the
parent cell. The daughter cells are not genetically identical, and neither is identical
to the parent cell.
Before meiosis begins, mitosis occurs up through anaphase. Therefore, we have
duplicated the chromosomes, they have separated, and moved to opposite ends of the cell.
But before the nuclear envelop surrounds them, they will go through another
chromosome pair separation without making a copy first.
Meiosis starts right after anaphase. Instead of going into telophase, the chromosome pairs
get ready to divide again. But this time, instead of making a duplicate copy of themselves
first, the chromosome pairs just merge and exchange genetic material, called
“crossing over”. This recombines the genes so that the new cells will not be identical to
the parent cell.
Then the chromosome pairs separate (This creates all sorts of possible combinations of
new chromosomes to occur in the daughter cells).
Then the chromosomes separate again (like in metaphase and anaphase).
Then the nuclear envelope appears and the cytoplasm pinches off (like in telophase),
leaving us with four daughter cells. Each of the daughter cells only has half of the
number of chromosomes as the original cell.
The daughter cells that are formed are sperm cells in males and egg cells in females
(these are gametes because each one has half the number of chromosomes). When a
sperm and egg combine and contribute their chromosomes, the fertilized egg (called
a zygote) will now have 23 pairs of chromosomes.
Nondisjunction
This is when chromosomes can become abnormal if the sister chromosomes do not
separate properly during meiosis in the formation of a sex cell. This is what causes a
sex cell to wind up with XXY or other chromosome abnormalities.
SUMMARY:
HEREDITARY PHYSICAL CHARACTERISTICS
Genotype and Phenotype
Genotype means the type of genes a person has, or their genetic make-up.
Those genes that affect the same trait are called alleles.
A dominant allele is given a capital letter, and a recessive allele is given the same letter in
lower case. For instance, having an earlobe that is unattached to the face is a dominant trait,
so we can call it E. An attached earlobe would then be called e.
Alleles occur in pairs; just as one pair of each type of chromosome is inherited from each
parent, so too each pair of alleles inherited from each parent.
The allele which is traditionally indicated by an uppercase (capital) letter is the
dominant trait. The allele which is traditionally indicated by a lowercase (small)
letter is the recessive trait.
If a sperm cell has e and the egg cell has e, the offspring must have ee. That is called
homozygous (pure) recessive. That means the person would have an attached earlobe.
If a sperm cell has E and the egg cell has E, the offspring must have EE. This is called
homozygous (pure) dominant. That means the person would have an unattached
earlobe.
The term for “pure” is homo. It refers to something being the same. The old days, you
had to shake up milk because the cream would rise to the top. Nowadays, people want
less fat, so the cream is removed before you get it; this is called homogenized milk. A
homogenized mixture is one that is the same throughout, and requires no periodic mixing.
Therefore, when the allele pairs are either EE or ee, they are homozygous.
The opposite of homo is “hetero”, so an allele pair that is “Ee” is heterozygous.
If one of the sex cells has E and the other sex cell has e, what will the offspring have? Ee.
What type of earlobe will they have? Attached. Why? Because the dominant trait is
stronger, so if it is present at all, it will manifest.
The physical appearance of a person is called the phenotype.
A person with Ee will therefore be called a heterozygous genotype, with an
unattached earlobe phenotype.
What earlobe alleles will a person have who is homozygous recessive? ee
What earlobe alleles will a person have who is homozygous dominant? EE
What earlobe alleles will a person have who is heterozygous? Ee
Figuring the Odds
If one of the parents is homozygous dominant (EE), the chances of their having a child
with unattached earlobes is 100 %, because this parent has only a dominant allele (E) to
pass on to the offspring. On the other hand, if both parents are homozygous recessive
(cc), there is a 100% chance that each of their children will have attached earlobes.
However, if both parents are heterozygous, then what are the chances that their
child will have unattached or attached earlobes? To solve a problem of this type, it is
customary first make a table of the genotype of the parents and their
E e possible gametes.
E EE Ee
e Ee ee
That means that when Harry meets Sally, their child has a 25% chance (1:3) of being
ee, and 25% chance of being EE, and 50% chance (1:1) of being Ee.
But that’s just the genotype. What about the phenotype (what will the child look like)?
There is a 75% chance (3:1) of having an attached earlobe (ee).
Example test questions:
In crossing a heterozygous parent and a homozygous recessive parent, what are the
chances that an offspring will receive a dominant allele? Answer = 50%
Do identical twins have identical DNA?
Identical twins, formed when one fertilized egg splits, are the only people in the world with
identical DNA. Fraternal twins, on the other hand, are formed when two different eggs are
fertilized. Genetically speaking, fraternal twins are no closer than normal siblings, sharing only
about 50% of their genes.
Although identical twins have the same genotype, or DNA, they have different phenotypes,
meaning that the same DNA is expressed in different ways.
Traits determined by phenotype include fingerprints and physical appearance. Thus, a DNA test
can't determine the difference between identical twins, while a simple fingerprint can.
What causes dimples?
All you need is one dominant gene to inherit a particular trait, including dimples, freckles, a
widow's peak, a cleft chin, and bushy eyebrows.
Does a blood transfusion change your DNA?
White blood cells do contain DNA. However, most blood transfusions involve only red blood cells,
which do not contain DNA. And even in a rare whole blood transfusion, no traces of foreign DNA
from the white blood cells have been detected in a recipient's blood.
On the other hand, there is at least one situation in which a transplant can change your DNA.
After a bone marrow transplant, the DNA in a blood sample may actually reflect the donor rather
than the recipient. That's because in this case, blood stem cells are transferred. The recipient will
produce blood that contains the donor's cellular elements but almost none of his or her own DNA.
And yes, this would affect DNA blood evidence (though there are other ways to test for DNA.)
Why am I right-handed, but my brother is left-handed?
Only 5% to 30% are left-handed. No one's sure if left-handedness is genetic, a learned behavior,
caused by prenatal or birth trauma, or if it's some combination of these factors.
There is only an indirect genetic cause for left-handedness.
If both parents are right-handed or if only the father is left-handed, a child has a 1 in 10 chance of
being left-handed. If only the mother is left-handed, the odds rise to 2 in 10. If both parents are
left-handed, the child has a 4 in 10 chance of being left-handed. So, while left-handedness might
be passed from parent to child, the chances are still greater that a child will be right-handed.
Identical twins have identical genes and, if handedness were wholly genetic, both twins would be
either right- or left-handed. But in studies of left-handed twins, only 76% of the pairs were both
left-handed. Others studies suggest that men are 1.5% to 4% more likely to be left-handed than
women.
GENETIC DISORDERS
Down Syndrome
Down syndrome is also called trisomy 21 because the person’s chromosome number 21
has three chromosomes joined together instead of just two. The chances of a woman
having a Down syndrome child increase rapidly with age, starting at about age 40.
The frequency of Down syndrome is 1/ 800 births for mothers under 40 years of age, but
women over 40 are 10 times more likely to have a Down syndrome child.
Characteristics of Down syndrome include a short stature; an eyelid fold; stubby
fingers; a wide gap between the first and second toes; a large, fissured tongue; a round
head; a palm crease (the so-called simian line), and mental retardation, which can
sometimes be severe. Their personalities are usually cheerful, good-natured, and pleasant
throughout their lives.
Amniocentesis (removing fluid and cells from the amniotic sac surrounding the
fetus) followed by karyotyping can detect a Down syndrome child.
Scientists have located genes most likely responsible for the increased tendency
toward leukemia, cataracts, accelerated rate of aging, and mental retardation. One day it
might be possible to control the expression of that gene even before birth so that at least
this symptom of Down syndrome does not appear.
Cri du Chat Syndrome (“cat’s cry”)
This is caused by one missing chromosome 5 and occurs in 1/ 50,000 live births. An
infant with this syndrome has a moon face, small head, and a cry that sounds like the
meow of a cat because of a malformed larynx. An older child has an eyelid fold and
misshapen ears that are placed low on the head. Severe mental retardation becomes
evident as the child matures.
Sex Chromosomal Disorders
All of the cells in our body have all of our chromosomes in the nucleus except for the egg
and the sperm. Each of these has all of our chromosomes in the nucleus, except there is
only one of the two sex chromosomes. Since women are XX, all of her egg cells are X,
but since males are XY, a sperm can bear an X or a Y. Therefore, the sex of the
newborn child is determined by the father. If a Y. bearing sperm fertilizes the egg,
then the XY combination results in a male. On the other hand, if an X-bearing sperm
fertilizes the egg, the XX combination results in a female.
All factors being equal, there is a 50% chance of having a girl or a boy. If a couple has
10 children and they are all boys, what is the chance that an eleventh child is going to be
a boy? Interestingly, the death rate among males is higher than for females. By age 85,
there are twice as many females as males.
Jacob syndrome occurs in 1/ 1,000 births. These XYY (an extra male chromosome)
males are usually taller than average, suffer from persistent acne, and tend to have
speech and reading problems. At one time, it was suggested that these men were likely
to be criminally aggressive, but it has since been shown that the incidence of such
behavior among them may be no greater than among XY males.
Klinefelter syndrome occurs in 1/ 1,500 births. These males with XXY (an extra
female chromosome) and they are sterile. They are males with some female
characteristics. The testes are underdeveloped, they have some breast development,
and there is no facial hair. They are usually slow to learn but not mentally retarded.
Triple-X syndrome occurs in 1/ 1,500 births. These are females with an extra female
chromosome: XXX. You might think they are especially feminine, but this is not the
case. Although in some cases there is a tendency toward learning disabilities, most have
no physical abnormalities except that they may have learning disabilities, menstrual
irregularities, including early onset of menopause.
Turner syndrome occurs in 1/ 6,000 births. The individual is XO, meaning one of the
sex chromosomes is missing. These are females and have a short, have a broad chest,
and webbed neck. The ovaries and uterus are nonfunctional. Turner females do not
undergo puberty or menstruate, and there is a lack of breast development. They are
usually of normal intelligence and can lead fairly normal lives, but they are infertile
even if they receive hormone supplements.
Dominant Disorders (only one dominate allele needs to be present)
Neurofibromatosis
Also known as Elephant Man disease, this is one of the most common genetic disorders.
It affects roughly 1/ 3,000 people. It is seen equally in every racial and ethnic group
throughout the world.
At birth or later, the affected individual may have six or more “coffee with milk”
colored spots (known as cafe-au-lait) on the skin. Such spots may increase in size and
number and may get darker. Small benign tumors (lumps) called neurofibromas may
occur under the skin or in various organs.
In most cases, symptoms are mild, and patients live a normal life. In some cases,
however, the effects are severe. Skeletal deformities, including a large head, are seen, and
eye and ear tumors can lead to blindness and hearing loss. Many children with
neurofibromatosis have learning disabilities and are hyperactive. The abnormal gene is on
chromosome 17.
Huntington Disease
This affects 1/ 20,000 people. It is a dominant neurological disorder that leads to
progressive degeneration of brain cells, which causes severe muscle spasms and
personality disorders. Most people appear normal until they are of middle age and have
already had children who might also be stricken. There is no effective treatment, and
death comes ten to fifteen years after the onset of symptoms.
Homozygous Recessive Disorders (both parents must have rr alleles)
Tay - Sachs disease
This disease usually occurs among Jewish people. At first, it is not apparent that a baby
has Tay-Sachs disease. However, development begins to slow down between four months
and eight months of age, and neurological impairment and psychomotor difficulties then
become apparent. The child gradually becomes blind and helpless, develops
uncontrollable seizures, and eventually becomes paralyzed. There is no treatment or
cure for Tay-Sachs disease, and most affected individuals die by the age of three or four.
It is caused by a genetic enzyme deficiency.
Cystic Fibrosis
This is the most common lethal genetic disease among Caucasians in the United
States.
About 1 in 20 Caucasians is a carrier, and about 1/ 2,500 births have the disorder. In these
children, the mucus in the bronchial tubes is particularly thick and interferes with
breathing, and the lungs get infected frequently.
New treatments have raised the average life expectancy to 28 years of age. The cystic
fibrosis gene is located on chromosome 7.
Phenylketonuria (PKU)
This occurs in 1 / 5,000 births, so it is not as frequent as the disorders previously
discussed, however, PKU is tested for in routine blood screenings of all newborns in
the United States. This is the disease that offspring of first cousins are more likely to
get.
PKU people lack an enzyme that is needed to break down an amino acid
(phenylalanine), and so the amino acid accumulates in the urine. These people have to
have a special diet that does not contain that amino acid. If they get too much of it, they
will get neurological problems and mental retardation. That’s why nutrition labels have to
warn when they contain phenylalanine.
Incompletely Dominant Traits
Incomplete dominance is exhibited when there is an intermediate phenotype. These
people can be carriers of a disorder without being sick themselves. Their children may
have the disorder, or they also may be carriers. When they are carriers, they are said to
have the “trait” of the disorder, but not the disease.
Sickle-Cell Disease
This is an incompletely dominant disorder. In persons with sickle-cell disease, the red
blood cells aren’t round disks like normal red blood cells; they are irregular. In fact,
many are sickle shaped, like a banana with points on both ends. The red blood cells do
not carry oxygen well, and they get stuck in arteries also.
Therefore, they suffer from poor circulation, anemia, poor resistance to infection, internal
bleeding, pain in the abdomen and joints, and damage to internal organs.
In malaria-infested Africa, infants with sickle-cell disease die (they got a bad
chromosome from both parents), but infants with sickle-cell trait (they got a bad
chromosome from only one parent) actually have better resistance to malaria than a
normal human being. The malaria parasite normally reproduces inside red blood cells.
But a red blood cell of a sickle-cell trait infant kills the parasite.
Therefore, the only people who survive in Africa well are those with sickle cell trait.
That’s why about 60% of the population in malaria-infested regions of Africa has sickle
cell trait. Unfortunately, 25% of their offspring can get the sickle cell disease.
Sex-Linked Traits
Traits controlled by alleles on the sex chromosomes are said to be sex-linked; an allele
that is only on the X chromosome is X-linked, and an allele that is only on the Y chromosome is Y-linked. Most sex-linked alleles are on the X chromosome since it is larger.
X-Linked Disorders
X-linked conditions can be dominant or recessive, but most known are recessive.
More males than females have the trait.
If a male has an X-linked condition, his daughters are often carriers, so her male
children are also likely to have the condition.
Male Pattern baldness is from a gene that is inherited from the mother. For you guys, if
your mother’s father was bald, you are more likely to be bald. It doesn’t matter if your
father is bald or if his father is bald. You get the baldness gene from your mother’s father.
Three well-known X-linked recessive disorders (more common in males than
females) are color blindness, muscular dystrophy, and hemophilia.
Color Blindness
In the human eye, there are three different types of cone cells (remember, they sense
color vision). These different types are sensitive to either the color red, green, or blue.
The gene for the red and green cells is on the X chromosome.
COLOR BLINDNESS TEST
About 8% of Caucasian men have red-green color blindness. Opticians have special
charts by which they detect those who are color blind.
Muscular Dystrophy
As you can tell by the name, this disease is characterized by a wasting away of the
muscles. The most common form is X-linked and occurs in about 1/ 3,600 male births.
Symptoms, such as waddling gait, toe walking, frequent falls, and difficulty in rising,
may appear as soon as the child starts to walk. Muscle weakness progresses to the point
where they need a wheelchair. Death usually occurs by age 20; therefore, affected
males are rarely fathers. The disease is from a carrier mother to carrier daughter.
Hemophilia
About 1/10,000 males is a hemophiliac. It is due to the absence of a clotting factor. It is
called the bleeder’s disease because the blood does not clot. Every time they get a bruise,
they have to have either a blood transfusion or an injection of a clotting protein, which
they keep in their refrigerator since they need it so often.
In the early 1900’s, hemophilia was prevalent among the royal families of Europe, and all
of the affected males could trace their ancestry to Queen Victoria of England. Of her 26
grandchildren, five grandsons had hemophilia and four granddaughters were carriers.
Because none of Queen Victoria’s forebears or relatives were affected, it seems that the
faulty allele she carried arose by mutation either in Victoria or in one of her parents. Her
carrier daughters, Alice and Beatrice, introduced the gene into the ruling houses of Russia
and Spain, respectively. Alexis, the last heir to the Russian throne before the Russian
Revolution, was a hemophiliac. There are no hemophiliacs in the present British royal
family because Victoria’s eldest son, King Edward VII, did not receive the gene and
therefore could not pass it on to any of his descendants.
Sex-Influenced Traits
The length of the index finger is sex-influenced. In females, an index finger longer than
the fourth finger (ring finger) is dominant. In males, an index finger longer than the
fourth finger seems to be recessive.
ABO Blood Types
A person’s blood type is determined by multiple alleles.
Three alleles for the same gene control the inheritance of ABO blood types.
These alleles determine the presence or absence of a particular protein on the red blood
cells.
A = “A” protein on red blood cells
B = “B” protein on red blood cells
AB= Both A and B proteins are on red blood cells
O = Neither A nor B protein on red blood cells
Blood typing can sometimes aid in paternity suits. However, a blood test of a supposed
father can only suggest that he might be the father, not that he definitely is the father. For
example, it is possible, but not definite, that a man with type AB blood is the father of a
child with type O blood. On the other hand, a blood test sometimes can definitely prove
that a man is not the father. For example, a man with type AB blood cannot possibly be
the father of a child with type O blood. Therefore, blood typing tests can be used in
legal cases only to exclude a man from possible paternity. However, DNA tests can prove
paternity.
Example test question:
If one parent has type A blood and the other has type O blood, what blood type
might the child have? Answer: A or O