Download Karyotypes and Genetic Disorders

TOPIC: Genetics
AIM: What is the gene
chromosome theory? How
do genetic disorders occur?
TOPIC: Genetics
AIM: How do genetic disorders
occur?
DO NOW: Write the
complimentary DNA strand
that would be attached to the
one below:
CTAACCGAG
Chromosomes & Genes…
• The human DNA code is made up of about three
thousand million A,T, C, and Gs on each side of the
DNA strand.
• If one were to recite the ATCG sequence in one's
DNA which is 3 billion long and would utter at a rate
of 100 ATCG sequences per minute without taking a
break for sleeping, eating or drinking, one would
speak for 57 long years.
Genetics: chromosomes & inheritance Untitled Page
Sex
•2
chromosomes
of 46 in
each cell
•X & Y
• Eggs = X
• Sperm = X or Y
•XX = female
•XY = male
Female chromosomes
Male chromosomes
inherited • Genetic disorders
diseases • Caused by genetic
mistake
• Caused by mutations
mutation • Change in gene or
chromosome  new
trait
• Can only be passed on to
offspring if in sex cells
Deletion
Duplication
Insertion
Translocation
Examples:
1. Addition:
GTACA  GTGCA
2. Insertion:
ATG GTC
 AAT GGT C
3. Deletion:
ATG GTC TCA AGG TCT CA
• Nondisjunction =
• Chromosomes don’t separate
properly during meiosis
• RESULT: some cells have too
many, some cells have too little
Harmful • May cause
Mutations various diseases
& disorders
Helpful •Cause
mutations
desirable
traits
•Examples:
• Potatoes =
• Resistant to disease
• Look and taste better
• Bacteria =
• Become more resistant to
antibiotics that kill them
•Seedless
oranges
Bardet-Biedl Syndrome is a rare genetic disorder that
affects many parts of the body. Only about 1 in 100,000
children have the disease, but those who do have it have
multiple disorders in development throughout their bodies.
A kitten named Cy was born with a defect called
holoprosencephaly. Animals born with holoprosencephaly
are born with one eye and an unformed brain. Little Cy,
adorable despite his deformity, sadly lived less than
twenty-four hours after his birth.
A piglet owned by Llu Shuping, a pig farmer in Northwest
China, has one head, two mouths, two noses, and three
eyes. In China the little misfit is a television celebrity.
A two-headed turtle calls an Aquarium in
Pennsylvania home.
A genetic mutation has left this small kitten born in Perth,
WI with two complete faces. Despite its deformities it is
an affectionate kitten that constantly purrs with
happiness.
The two-headed calf born in
Iowa, US in April 1998 had four
eyes and three ears and was
appropriately named
Reflections.
One-eyed frog
Two-headed
python
Three-legged
duck
Five-legged
lamb
Frog
With
Mutation
Venus Fly
Trap with 2
traps
Six-legged
fawn
Left: A normal fruit fly
Right: A fruit fly with its legs growing out of its
head. This is a mutation caused by radiation.
Genetic Disorders
1. Sickle • Blood disorder
cell • Caused by
anemia mutation
• Red blood cells
change shape
• Cannot obtain enough
oxygen
• Clump together and clog up
blood vessels
2. Down • Caused by
Syndrome NONDISJUNCTION
• Extra copy of
chromosome 21
• Trisomy 21
Down syndrome (DS) causes delays in the way a child develops, and often leads
to mental retardation, which means they may have trouble learning. It affects
1 in every 800 babies born. You have probably seen people who have DS. They
have certain physical features, such as a flatter face & upward slanting eyes.
It's important to note, though, that not all people with DS look alike or have
all these features. They may have medical problems such as heart defects.
Kids with DS can go to regular schools, make friends, enjoy life, and get jobs
when they're older. DS affects kids' abilities in different ways. Kids with DS
can and do learn, and are capable of developing skills throughout their lives.
They simply reach goals at a different pace. Kids with DS have a wide range
of abilities, and there's no way to tell at birth what they will be capable of as
they grow up.
How can genetic
disorders be
detected?
• 1. AMNIOCENTESIS =
• Long needle removes amniotic
fluid
• Fetal cells are tested
• 2. KARYOTYPE =
• Picture of all chromosomes in a
cell
Female = XX
Male = XY
Down Syndrome
Review:
1. What two sex chromosomes do all
males have?
2. Explain what a mutation is.
3. In order for a mutation to be passed
on to offspring, where must it occur?
4. What causes Down Syndrome to
occur?
5. What is a karyotype?
Klinefelter Syndrome occurs in 1 in 500 to 1 in 1000
births. Men and boys with Klinefelter Syndrome have a Y
chromosome and 2 X chromosomes. They develop as males
with subtle characteristics that become apparent during
puberty. They are often tall and usually do not develop
secondary sex characteristics such as facial hair, or
underarm and pubic hair.
Trisomy 13 is a very
severe genetic disorder
with early death. The
babies frequently have
cleft lip and palate, and
congenital heart
malformations.
Trisomy 18 (Edwards
syndrome) is a serious
syndrome where the babies
generally die in the first life
year. The babies have
malformations of many
organs.
Turner syndrome (TS) affects about
1 in every 2,500 girls. They are born
with only 1 X chromosome. Girls with
TS are usually short in height (about
4’7”). When diagnosed while still
growing, they can be treated with
hormones to help them grow taller.
TS prevents the ovaries from
developing properly, which affects a
girl's sexual development. Most won’t
go through all changes associated
with puberty unless they get
treatment, and will be unable to
become pregnant on their own. Other
features may include a "webbed"
neck, a low hairline at the back of
the neck, drooping of the eyelids,
differently shaped ears that are set
lower on the sides of the head than
usual, and abnormal bone
development (especially the bones of
the hands and elbows).
Cri du Chat Syndrome ("Cry of the cat" in French) is a genetic disorder
(1 in 50,000 live births) caused by the a missing part of the 5th
chromosome. It was first identified in 1963 and named after the sound
that many of the babies and children make when crying. The cry is
caused by abnormal larynx development, which becomes normal within a
few weeks of birth. Infants typically have low birth weight, slow growth,
a small head, and poor muscle tone. They may have congenital heart
defects. Individuals with cri du chat syndrome have language
difficulties, delayed motor skill development, and mental retardation.
Behavioral problems may also develop as the child matures.
Cri-du-chat Syndrome
Tay-Sachs Disease
• Caused by mutation
• Gene is recessive (both parents must carry gene)
• Abnormal gene stops the body from making an enzyme that
breaks down fat
• Fat gathers in the brain  brain damage and death
Tay-Sachs disease (TSD) is an inherited, incurable
disease of the central nervous system. Symptoms
first appear at about 6 months, when an apparently
healthy baby stops smiling, crawling or turning over,
loses their ability to grasp or reach out, and gradually
becomes blind and paralyzed. There is no cure and
death usually occurs before the age of five.
Cystic Fibrosis
• Caused by mutation (recessive)
• Body makes abnormally thick mucus in the lungs &
intestines
• Can lead to infection by bacteria, lung damage
Cystic fibrosis affects more than 30,000 children and young adults in the
United States. It can be mild or severe, depending on the person. To make
normal mucus, the body needs a special protein. This protein is defective in
cystic fibrosis, producing the thick, sticky mucus that causes problems for
people with CF. Doctors may suspect that a baby has CF if he or she coughs
a lot and gets a lot of lung infections. The baby also might have unusual
large, bulky bowel movements or may not gain weight as expected.
PKU
• Phenylketonuria
• Caused by a mutation (recessive)
• Missing important enzyme
• Can’t break down certain chemicals in food
• Leads to build up  brain damage
High amounts of phe in the body can lead to mental retardation, seizures or
convulsions, eczema, and an unusual odor in the urine. PKU is treated with a
special diet that limits the amount of phe eaten. Foods high in protein (milk,
eggs, meats, fish, cheese), aspartame, & wheat products containing gluten (high
in protein), can’t be eaten if a person has PKU. This way, blood phe levels can
be reduced. Since phe is an essential AA, it shouldn’t be totally omitted from
the diet. A person with PKU has to drink a special formula every day which has
the necessary ingredients for the body's growth and development but contains
very little or no phenylalanine. It contains the right amounts of essential amino
acids other than phe.