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Chapter 14 Lecture
Human Heredity
During metaphase of mitosis, scientist takes a picture of the chromosomes. This is called a karotype. A karotype
should contain 46 chromosomes, 23 pairs. The 23rd pair is the sex chromosomes; the other 22 pairs are called
autosomes. Males would be 46XY, female’s 46XX notice, on pg. 341, the size difference between the X and Y
chromosome. There is always a 50/50 change of being a male or female.
X
X
X
Y
When you look at inheritance from one generation to the next, you use a pedigree chart
Female
Male
Female Carrier
Male Carrier
Female with Trait
Male with Trait
Create a pedigree chart based on albinism.
A couple has a normal pigment son and an albino son. The albino son marries a normal pigment female they have 7
children. One male and one female of the 7 children are albinos.
Color in all the possible carriers.
Is that a dominant of recessive trait? _________________________
If the albino granddaughter marries a homozygous dominant man, how many of her offspring will be
albino?____________________
Human Genes
Blood: Rh gene has two alleles, + and -.
Blood type is A, B, O. A and B are co – dominant and O is recessive.
AA, AO,
A
Give blood A
B
O
AB,
AB
BB, BO,
B
O
A, AB,
B, AB,
A, AB, B, O
Receive blood from A receive from A,O
B receive from B,O
AB receive from ALL
O receive from O
OO
Dominant Alleles
As you know, a capital letter indicates a dominate allele, if one person has a dominant genetic disease such as
Huntington’s then it will e passed on to 50% of children.
H
h
h
h
Recessive alleles
Cystic Fibrosis is a recessive allele that causes severe digestive problems. They over produce mucus and the
mucus is so thick is clogs the lungs. A part of chromosome 7 is missing and the DNA doesn’t code for a transport
protein in the plasma membrane. The transport protein (channel protein) allows Cl- ions into the cell.
Sickle cell
RBC’s are not round and do not carry oxygen. They also block blood vessels.
SS= normal
Ss= normal, resistant to malaria
ss= sickle cells
S
s
S
½ children will not get malaria.
s
Human genes on chromosomes
Human DNA is 6 billion base pairs long. All 6 billion fit in 46 chromosomes. Chromosomes 22, the smallest
one, have 43 million base pairs. There are 545 identified genes on this smallest chromosome, including one that
causes leukemia and neurofibromatosis (makes tumors).
Non disjunction occurs where there are more or less chromosomes than 46. Trisomy 18 or 21 is downs
syndrome. There are three chromosomes on 21st, or 18th chromosome.
Turners= XO, sterile
Kleinefelters= XXY, sterile
Sex Determination
There are 22 pairs of chromosomes are 2 sex chromosomes. The 22 pairs are called autosomes and are
homologous. They look exactly alike.
The sex chromosomes look like XX for female and XY for male. Sperm are either X or Y.
Female Eggs are always ___________
Number of boys________
Number of girls ________
Probability of first child being a boy ________
Probability of first child being a girl __________
Sex Linked Inheritance
Drosophila or fruit flies have red eyes. A scientist named Dr. Morgan noticed that one male had ________
eyes. Only males have white eyes. See page 337. Eventually Morgan bred a white-eyed female and proved eye color
is found on the X chromosome. After fertilization there will always be a 1:1 ratio of male female.
Sex linked inheritance occurs when the traits or genes are located on X or Y chromosomes. A small subscript indicates
the trait. Fruit flies generally have red eyes, but a male fruit fly may have white eye due to a sex linked trait. XRXR x
XrY
Red eyed males ______ Red eyed females _______
White eyed males_____ White eyed females _______
F1= _________red eyes
Cross F1 male x F2 female =XR
Red males ___________ Red eyed Females __________
White eyed males _________ White eyed females________
F2=
_____females red eyes, _______females white eyes
_____males red eyes _______males white eyes
In this case the dominate allele is carried on X chromosomes and will only show up in males because males
only have one X chromosome. The females have two X chromosomes and always have at least one dominant X.
Morgan eventually produced a white eyed female and crossed it with a red eyed male.
F=1 Female are ________red-eyed, ______ males whiteeyed
F2 generation crossed with a white eyed male x red eyed female
Morgan concluded only the X chromosomes have the allele for eye color in flies, the y chromosomes had no effect.
Human Sex Linked Traits
Genes that are found on the X + Y chromosomes are called sex linked. 100 disorders are found on the X
chromosome. Males have only one X, so if that X has a genetic disorder, the male does not have another dominant
X to mask the disorder. Therefore the male will have this disease. Rarely do females have sex-linked diseases. If a
female has it, it means that both of her X chromosomes have the trait. Very few females are color blind.
Problem
A Husband and Wife Marry. The husband is colorblind. They have four children; one daughter and one son are
colorblind. List all possible carriers.
Problem
Two people marry and have six children, the last two, of which are boys.
One boy has hemophilia and dies. The other boy does not have hemophilia.
The four daughters marry.
The second born daughter has a daughter and then has a son with hemophilia.
The fourth daughter has three sons, one of which has hemophilia.
The daughter of the second born daughter marries and has a son and a daughter with hemophilia.
Gene Therapy—an absent or faulty gene is replaced by a normal, working gene. How do you add a gene? Viruses
already do this. A virus will attach to a cell, insert its own DNA into the cell and our cells start making the virus instead
of being a healthy cell.
This same virus is stripped of its’ DNA and has the good gene inserted. The virus will attach to the cell, but insert a
good gene into the cell.
Ethics
Do you think it is reasonable to choose the traits of your child?
If you were a carrier for a genetic disorder, would you choose to have children?
Polygenic Inheritance: traits governed by name different chromosomes. Each allele is represented by an uppercase
letter and equally expressed. Stem length has 3 alleles. A, B and C
By crossing a 10 cm Tall plant AaBBCc x aabbcc you can get many different combinations and heights.
Aa or aa, Bb or bb, Cc or cc
Other things also influence traits, such as the ____________________, hormones, and age. Fur of rabbits
change color in the winter. Males are larger due to testosterone. Animals weight more when food in abundant.
Applied genetics
How do you determine if an organism is homozygous dominator heterozygous? You must run a test cross.
You cross an unknown with the known genotype. The easiest way is to test with homozygous recessive. When
breading an animal they might be a carrier for the disease or trait that is undesirable. The phenotype for the carrier or
homozygous dominate is the same.
In dogs, long legs are dominant to dwarf legs. Determine if your husky is a carrier for dwarfism.
A couple wants to have children, but both families are carriers for a certain recessive disease. Predict their
children’s genotype.
Shot gun Sequencing
Fragment A: GATCTAGGTCATG
Fragment B: ACAG
Fragment C: CAGTCTGATC
Fragment D: AGGTC
Fragment E: CATGCGATC
Chapter 14 Terminology
* Be able to make a pedigree and read a pedigree.
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Male Symbol
Female Symbol
Male Carrier Symbol
Female Carrier Symbol
Expressed Male Trait
Expressed Female Trait
Karyotype
Autosomes
Sex Chromosomes
Male Chromosomes
Female Chromosomes
Non-Disjunction
Pedigree
Polygenic
Sex Linked
Example of Sex Linked
Dominant Genetic Disorder
Example of Dominant Genetic Disorder
Turner’s Syndrome
Karyotype Example of Turners Syndrome
Klinefelters Syndrome
Karyotype example of Klinefelters Syndrome
# of chromosomes in a normal human male
# of chromosomes in a normal human female
Universal blood donor
Universal blood recipient
Can only receive A or O blood
Can only receive B or O blood
OO (iOiO)
__1___
___3__
___5__
___2__
___4__
__7___ Picture of Chromosomes arranged in homologous pairs
__8___ The first 22 pairs of human chromosomes
__9___ The 23rd pair of human chromosomes
__11___ XX
__10___ XY
__12___ Homologous chromosomes fail to separate during meiosis
__13___ Chart that shows the relationships and traits within a family over several generations
__14___ Trait controlled by many genes
__15___ A gene that is found on the sex chromosomes
__16___ Hemophilia, Color blindness,
__17___ A disorder that will show up 50% of the time in each generation
__18___ Huntington’s Disease, Achondroplasia Dwarfism
__19___ Occurs from non disjunction, only 45 chromosomes
__20___ 45 XO
__21___ Occurs from non disjunction, with extra sex chromosomes
__22__ 47 XXY
__24___46XX
__23___46XY
__25___ OO
(iOiO)
__26___ AB
( IA I B )
__27___ A
(IAIA, IAiO)
__28___ B (IBIB, IBiO)
__29__ Can only receive O blood
__6___