Download Unit 9 Human Genetics

Name ___________________________________ Per. ________
Test Date ___________
Unit 9- Human Genetics
Monday Jan. 23
Tuesday Jan 24
Block Day Jan. 25/26
Friday Jan. 27
Monday Jan. 30
Tuesday Jan. 31
Block Day Feb. 1/2
Friday Feb. 3
TestUnit 9 Human Genetics
Prior Knowledge Needed
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Review what somatic cells are and
where you would find them.
Review what gametes are and where
you would find them, and where they
are made.
Basic Genetic Vocab
Punnett Squares
Looking at Human Chromosomes & What can go
wrong:
 Identify how karyotypes are used to study
genetic disorders
 Analyze different karyotypes to identify if it
is a normal vs disorder
 Understand how nondisjunction is related to
Down Syndrome and other abnormal
Chromosomal numbers disorders
Using Punnetts & Pedigrees for autosomal
disorders:
 Understand and be able to predict “NonMendelian” genetics including incomplete
dominance, codominance, multiple alleles and
sex-linked. Using both Punnetts and
Pedigrees.
 Analyze traits over several generations by
using both dominant and recessive
pedigrees
 Identify different human Autosomal
genetic disorders including:
o Recessive: Cystic Fibrosis,
Albinism
o Co-Dominant: Sickle Cell Anemia
o Dominant: Huntington’s &
Achondroplasia
Using Punnetts and Pedigrees for Sex-Linked
Disorders:
 Identify different human Sex-Linked
disorders including:
o Color blindness, Hemophilia and
Duchenne’s Muscular Dystrophy.
 Analyze how Sex-linked traits are
passed on through several generations
by using a pedigree
UNIT 9 – HUMAN GENETICS
What are somatic cells?
Give an example:
What are autosomes?
How many autosomes do
humans have?
How many sex
chromosomes do we
have?
What are girls’ sex
chromosomes?
What are boys’ sex
chromosomes?
I. HUMAN GENETICS
(pp. 311-313)
A. Human Somatic Cells
 _body__ cells are _diploid___ or _2n___.
 Each cell contains _46___ chromosomes, or _23___ pairs of chromosomes.
o Of the 23 pairs 22 are homologous ,contain the same genes in the same
order, and are called autosomes.
o The 23rd pair of chromosomes are the sex chromosomes.
 Female= XX
 Male = XY
B. Human Gametes
a. Gametes are _haploid_, or _n__, and contain _23___ chromosomes.
b. Female gametes are _egg__ cells made in the ovaries in the process of meiosis
c. Male gametes are _sperm___cells made in the testes in the process of meiosis
d. Egg cells can only contain an X chromosome
e. Sperm cell produced has a _50__% chance of containing a Y and a _50__%
chance of containing a X.
o the _male___ determines the sex of the offspring.
What is Nondisjunction?
Where/When does
nondisjunction occur?
What type of mutation results
from nondisjunction?
Can these mutations be
inherited?
What is a Karyotype?
What is a Karyotype used
for?
C. Analyzing Human Chromosome Numbers
1. Nondisjunction - Abnormal numbers of chromosomes in gametes result in genetic
disorders called number disorders.
 Nondisjunction, which means _”not coming apart”.
 A chromosome pair fails to separate correctly in _anaphase so the
gametes produced have an abnormal _number of chromosomes.
 Number disorders are not inherited; therefore, they cannot be
predicted with _Punnett squares.
2. Karyotypes
 A photograph of _chromosome pairs__.
 Cells are stopped during mitosis and are stained, photographed and
the photograph is enlarged.
 The chromosomes are cut out and arranged in _homologous pairs in
size order, with the sex chromosomes making up the 23rd pair.
 Used to detect number disorders and to determine the _gender__ of
an unborn child.
 Do not detect abnormal genes; therefore, a normal karyotype does
not guarantee a _normal child!
II. HUMAN GENETIC DISORDERS – NUMBER DISORDERS
(pp. 313-314)
A. Autosomal Number Disorders
 Most are _lethal____.
What are autosomes?
 The only autosomal number disorder that allows survival into adulthood is _Down
syndrome____.
What are sex
chromosomes?
What autosomal number
disorder can produce a
living baby?
What does Trisomy 21
mean?
1. Down syndrome
 Known as _trisomy 21 because there are _3 chromosomes at the __21st_ position,
instead of _2___.
 Individuals have characteristic facial features; growth, behavior, and mental
development are all affected.
There is also a higher risk of _congenital____ heart defects.
The incidence of babies with Down syndrome is much higher in _older__ mothers.
What would result if
you got trisomy 19?


B. Sex Chromosome Number Disorders
1. Turner Syndrome
 Called _45 X0
What does it mean
when you have a sex
 Because
chromosome number
individuals lack 2nd
disorder?
sex chromosome
 Female, typically _short____
in stature, underdeveloped
sexually, _sterile, with a
What is the name of
normal life expectancy.
the Female sex
chromosome number
disorder?
What is the name of
the male sex
chromosome number
disorder?
2. Klinefelter Syndrome
 Called _47 XXY___.
 Symptoms do not appear until _puberty_
at which time affected _males show
poor sexual development and infertility.
 Treated with _testosterone___. Normal
life expectancy.
Homework Practice Problems
1. Is this child a Male or a Female? _________
Is this child a Male or a Female? _________
2. What is wrong with this child? ______________
What is wrong with this child? _____________________
3. Male or Female? ___________
Male or Female? ___________
4. What is wrong with this child? ______________
What is wrong with this child? ______________
5. Male or Female? ___________
Male or Female? ___________
6. What is wrong with this child? ______________
What is wrong with this child? _____________
7. Male or Female? ___________
Male or Female? ___________
III.
ANALYSIS OF HUMAN INHERITANCE
A. Punnett Squares & Multiple Alleles (pp. 304)
1. multiple alleles; _more than 2____ alleles.
 An example of this is ABO blood groups. There are _3____ alleles for this gene. Two of the alleles,
_A__ and B are co-dominant, meaning __they always show if present. The third allele, o, is
recessive, meaning it will only show if the genotype is _ii_.
 Each individual inherits 2_alleles for this gene, one from __mom____ and one from __dad_____.
The possibilities for blood group genotypes and phenotypes are:
Phenotype
Genotype
Type A blood IA IA or IA i
Type B blood
IB IB or IB i
Type AB blood IA IB
Type O blood
ii
1. A couple preparing for marriage have their blood typed. Both are AB. They ask you what types of blood their
children may have. What would you tell them?
Cross: __________________________________
Blood type is both
multiple allele and
co-dominant. Which
2 letters are codominant?
What does codominant mean?
How many blood
type letters are
there?
Phenotype Ratio: ________________________________________
2. An old, rich couple dies in an accident. Soon a man shows up to claim their fortune, saying he is the
long-lost son who ran away with a circus as a boy. Other relatives say he is lying. Hospital records
show the couple'’ blood types were AB and O. The claimant is O.
Cross: __________________________________
What are they?
Can a mom with A
blood & a dad with
B blood produce a
baby with O?
How?
Is he an imposter? _______________
2. 2 different couples gave birth at the same time. One baby has blood type O and the other
baby has blood type A. The nurses can not remember which baby goes with which parents.
The first set of parents, the Lam’s have blood type A & blood type B. The second set of
parents, the Buck’s have blood type A and blood type AB. Which baby belongs to which
parent?
Lam’s: baby with blood type __________
Buck’s: baby with blood type __________
Homework Practice Problems:
1. A person with type A blood (unknown genotype) marries a person with type O blood. What blood types are
possible among their children. (Show 2 crosses)
_____________________________
2. Two people with type O blood have three children. How many of those three children also have type O blood?
_____________________________
3. A woman with blood type B marries a man with blood type O. Is it possible to have a child with blood type A?
__________________
4. Mom has blood type AB and child has blood type A what could dad be? (list all that apply)
_________________________
5. Ralph has type B blood and his wife Rachel has type A blood. They are very shocked to hear that their baby has
type O blood, and think that a switch might have been made at the hospital. Can this baby be theirs?
_____________
6. Explain why or why not (use a Punnett square to help).
_________________________________________________
_________________________________________________
7. Both mom and dad have blood type AB. What are the possible outcomes of the children? ___________________
Alice has type A blood and her husband Mark has type B blood.
Their first child, Amanda, has type O blood.
Their second child, Alex, has type AB blood.
8. What is Alice’s genotype? _____________
9. What is Mark’s genotype? _____________
10. Candace has type B blood. Her husband Dan has type AB blood. Is it possible for Candace and Dan to have a
child that has O blood? ___________
11. Explain why or why not (use a Punnett square to help).
_________________________________________________
_________________________________________________
B. Pedigrees (pp. 299-301)
 A diagram that follows the inheritance of a single _trait___ through several
What is a Pedigree?
_generations_ of a family.
 Males are represented by _squares____
 Females, by _circles____.
In a Recessive pedigree
 Individuals with the trait are represented with _shaded____ figures.
all the shaded individuals
 Individuals shown with unshaded figures _do not show the trait___.
show what?
 Vertical lines connect _parents____ and _children____.
 Horizontal lines connect _spouses___ or
_siblings__.
In a Dominant pedigree
 Children are placed in _birth order__, from
all the shaded individuals
_left___ to _right_____.
show what?
So, in a dominant
pedigree do you want to
fill out the shaded
individuals or the nonshaded individuals first?
a.
b.
c.
d.
e.
1. The following pedigree shows the
inheritance of a recessive trait.
How many generations are shown in this pedigree? _______________
How many children did Parents I1 and I2 have? ________ How many boys? _______ Girls? ________
How many children did Parents II1 and II2 have? ________ How many boys? _______ Girls? ________
Key: _______________________________________________________________________
To solve a pedigree: Label all ________________________________________________ first!
2. Determine the genotype of all individuals in
this pedigree showing the inheritance of red hair,
a recessive
trait.
Key: _________________________________
3. Determine the genotype of all individuals in the
following pedigree showing the inheritance of a dominant
trait.
Key: __________________________
Homework Practice Problems:
1.
The following pedigree illustrates the inheritance of a recessive trait.
Identify the genotypes of each individual shown in the pedigree.
Key: __________________________________
2.
The following pedigree illustrates the inheritance of a dominant trait.
Identify the genotypes of each individual shown in the pedigree.
Key: ________________________________
3.
Examine the pedigree below showing the inheritance of albinism, a
recessive trait. Identify the genotypes of all individuals
a.
Key: ________________________
b.
If individual E marries a man with
albinism, what is the probability they
would have a child with the disorder?
Cross: ___________________________
c.
Probability: ______________________
d.
If this same couple (E x albino male) has a
child with normal pigmentation, what is
the probability their child is a carrier for
albinism? _________________________
4. The following pedigree if for neurofibromatosis, a dominant trait. Identify the genotypes of all individuals.
Key: ___________________________
IV. INHERITED HUMAN GENETIC DISORDERS
A. Gene Mutations
 a change in the DNA sequence of the gene_.
What are autosomes?
 Causes Inherited human genetic disorders
What are sex
chromosomes?
Autosomal disorders occur
where?
B. Types of Inherited Genetic Disorders
1. Autosomal Genetic Disorders – Gene mutation is on any chromosome other than
_sex chromosomes____.
2. Sex-Linked Disorders – Mutated gene is on the _X__ chromosome
V. GENETIC DISORDERS - AUTOSOMAL DISORDERS
(pp. 345-348)
 Most genes are carried on the _autosomes, _44___ chromosomes other than the
sex chromosomes.
 Most genetic disorders are _autosomal___ disorders.
 These disorders affect males and females _equally_ and are due to _gene___ mutations.
 Autosomal disorders can be divided into three groups based on the pattern of inheritance.
A. Autosomal Recessive Disorders (pp. 297)
1. Albinism – Characterized by failure to produce pigment, _melanin___. Affected individuals lack coloration in
_eyes, _skin, and _hair. Very susceptible to _UV light____. Symptoms appear _at birth; _Normal life expectancy.
2. Cystic Fibrosis – Characterized by excess _mucus production in _lungs_, digestive system. Symptoms appear
just after birth and include frequent respiratory infections, poor nutrition. With treatment, patients can survive to
young adulthood. Cystic fibrosis is the most common _fatal__ genetic disorder in the _United States___ among
Caucasians.
B. Autosomal Co-Dominant Disorders (pp. 303)
1. Sickle cell anemia is an autosomal co-dominant disorder that affects _hemoglobin___ production.
Hemoglobin is the protein that binds _oxygen____ to red blood cells.
a. Individuals with the normal genotype, AA, do not have the sickle cell allele and produce only normal
What does CoHemoglobin.
dominant mean?
So if you are
heterozygous for
sickle cell what
does that mean?
What does
Autosomal
Dominant mean?
b. Individuals that are SS produce abnormal hemoglobin that causes the red blood cells to “sickle”
when oxygen availability is decreased;
i. for example, in high altitudes or during periods of stress. Sickled RBCs are more fragile,
easily destroyed – results in lack of _energy____ due to decreased _ATP production in
cells, blockage of blood vessels, and severe pain. Shortened life expectancy. Most
common inherited disease in individuals of _African_ ancestry.
c. Heterozygotes (AS) produce both normal and abnormal hemoglobin and are said to have _sickle
cell trait___. They do not show symptoms of the disorder. In certain areas, individuals with sickle
cell trait have a benefit over individuals that lack the sickle cell allele because they are resistant to
_malaria____. Malaria is a serious, sometimes fatal disease spread by _mosquitoes___ that
affects millions of people each year in _Africa__. This increased malarial resistance has resulted in
a very high incidence of AS individuals. If two heterozygotes marry and have children, they have a
_25__% chance of having a child with sickle cell anemia.
C. Autosomal Dominant Disorders (pp. 298)
1. Huntington’s Disease – Fatal genetic disorder in which symptoms do not show until _30s to 40s___.
Characterized by deterioration of _nervous system_____.
2. Achondroplasia - _Dwarfism___
Homework Practice Problems:
Complete the following autosomal crosses:
1. Is Huntington’s dominant, recessive, or co-dominant? ___________________
2.
3.
If a male heterozygous for Huntington’s and a homozygous recessive female having a child with
Huntington’s?
a.
Phenotypic ratio: ______________________
b.
Genotypic ratio: _______________________
The following pedigree illustrates the inheritance of a Huntington’s Identify the genotypes of each individual shown in the
pedigree.
Key: ________________________________
4. Is Sickle Cell dominant, recessive, or co-dominant? ___________________
If you cross a man who is heterozygous (have both sickle cell and normal cell) with a woman who does not have sickle cell.
5.
6.
What percent of the offspring will have sickle cell? _______________
What fraction of the offspring will have both sickle cell and normal cells? __________________
7.
8.
Is Cystic Fibrosis dominant, recessive, or co-dominant? ___________________
If you cross two heterozygous parents for Cystic Fibrosis what is the chance of having a child with Cystic Fibrosis? ______
9.
The following pedigree illustrates the inheritance of a Cystic Fibrosis. Identify the genotypes of each individual shown in the
pedigree.
Key: ________________________________
VI. GENETIC DISORDERS - SEX-LINKED DISORDERS
A. Sex-Linked Inheritance (pp.305-308)
 “Sex-linked” if it is located on a sex chromosome (_X__ or _Y__).
 In humans, sex-linked genes are almost always located on the larger _X___
Where are Sex-linked
disorders found?
chromosome.
o The _Y chromosome is much smaller and carries only a few genes
So, if you are working
related to male _sexual development.
with sex-linked
o Females have __2__ X chromosomes;
disorders you must use
o Males have _one____.
________ for girls and
________ for boys.
 Females will only show recessive traits located on the X chromosome if they are
_homozygous recessive.
What is the only way
 Males will always show a recessive trait located on the X chromosome because
for girls to show the
he only has one X.
sex-linked disorder?
Why?
Why can girls be
carriers for sex-linked
disorders?
Can boys be carriers?
Why?
If a boy has the
disorder, which parent
did he get it from?
This results in _males___ having a much higher incidence of sex-linked disorders.
1. Genotypes for sex-linked traits are written using the X and Y chromosomes to show
path of inheritance.
 Example, male-pattern baldness is a sex-linked recessive trait. If H = normal
head of hair and h = baldness, bald male = _Xh Y_____; bald female = _ Xh Xh
___.
o Females can be __carriers___ for sex-linked recessive disorders = XH
Xh The defective allele does not show!
o Males _cannot_____ be carriers for sex-linked traits because
their 2nd sex chromosome is the _naked Y_!
2. Sex-Linked Punnett Squares –
 In sex-linked traits, probabilities for male and female offspring must be
calculated separately because traits are _inherited differently___.
If a man with a full head of hair marries a woman who is heterozygous, what is the
probability they would have a son who would go bald? A daughter?
Key: ______________________________________
Cross: _____________________________________
Probability of bald daughter = ___________
Probability of bald son = ____________________
B. Sex-Linked Disorders – All of these disorders are sex-linked _recessive_____.
1. Color Blindness – Inability to differentiate and distinguish _colors_____.
2. Hemophilia – Missing an enzyme required for normal _blood clotting_____ - results in _uncontrolled bleeding_.
Treated with blood transfusions, injections of missing factor.
3. Duchenne’s Muscular Dystrophy – Symptoms develop at _3 – 6 years______. Muscles _weaken, break down,
leading to eventual death. No available _treatment____ or _cure_. Death usually occurs before adulthood.
C. Examples
1. A colorblind female marries a man with normal vision. What is the probability of colorblind children?
Key: ______________________________________
Cross: _____________________________________
Probability of colorblind daughter = _________ Probability of colorblind son = __________
2. A genetics counselor interviews a couple with a family history of hemophilia to evaluate the possibility
of offspring with the disorder. The woman does not have hemophilia, but states that her father had
the disorder. The man is normal.
Key: ___________________________________________
Cross: ___________________________________
Probability of daughter with hemophilia = ___________
Probability of son with hemophilia = __________
3. The following pedigree shows the path of inheritance of hemophilia through several generations. Identify the
genotypes of each individual.
This is a Sex-linked
Recessive disorder, so
what needs to be used to
fill it out?
Boys= __________
Girls= __________
Are the shaded
individuals normal or do
they have hemophilia?
Who should you fill out
first, the boys or the girls?
Why?
Key: ________________________________________________________________
Homework Practice Problems:
1.
A hemophiliac man marries a woman who is a carrier of the hemophiliac condition. Draw a Punnett square representing the
offspring of this marriage.
a. What percentage of the offspring will be a hemophiliac? ___________
b.
Is it possible for these parents to produce an offspring that is neither a carrier nor a
hemophiliac? ______________
2.
c.
If so, would this individual be male of female? ___________
d.
What would be the genotype of this individual? __________
e.
Is it possible to have a female hemophiliac? _____________
In the case of the sex-linked gene responsible for hemophilia, a hemophiliac father never transmits hemophilia to his son.
Explain why: ______________________________________________________________________________________
3.
Red-green color blindness is also a sex-linked recessive trait in humans. Using B as the superscript for normal vision and b
for color blindness, give the genotypes for the following:
a. A normal female:____________________
d. A normal male: _____________________
b.
A carrier female: ____________________
c.
A color blind female: _________________
e. A color blind male: __________________
4.
A color blind male x a female carrier
Percent of boys who will be color blind: ___________
Fraction of girls who will be color blind: _____________
5.
Normal vision male x color blind female:
Percent of boys who will be color blind: ___________
Fraction of girls who will be carriers: _____________
6.
The following pedigree shows the path of inheritance of
genotypes of each individual.
a.
hemophilia through several generations. Identify the
Key: ________________________
7.
If individual III-2 marries an unaffected woman whose dad had hemophilia, what is the probability that their son will be
hemophilic? _______________ What about their daughter? _______________
8.
If individual III-3 marries a non-hemophilic male, what is the probability that they will have hemophilic daughters? _____
sons? _____