Download Name: Homework/class-work Unit#9 Genetic disorders and

Name: ____________________________ Homework/class-work Unit#10 Genetic disorders and pedigrees (25 points)
Think and try every question. There is no reason for a blank response or an I don’t know. Any blanks will receive a zero.
Every assignment must be done on a separate piece of paper. Each assignment must be complete, neat, in complete sentences
and done on time for full credit. Any assignment may be used as a take home or pop quiz at any time. One missing or late
assignment will lose 5 points, 2 will lose 15 points, 3 will be considered incomplete and given a zero.
1. Genetic disorders reading:
Date: __________________
Mechanism of transmission of genetic disorders:
Numerous human diseases result from genetic disorders. Some diseases are caused by
single gene mutations, whereas other diseases are due to abnormalities in chromosome
number or structure. Although chromosome abnormalities and mutations both cause
disease, they do so via different mechanisms, are diagnosed differently, and require
different potential treatments and precautions.
Sex Chromosomes Abnormalities
Chromosome abnormalities arise several different ways. If the sex chromosomes fail to
separate correctly during meiosis (chromosome nondisjunction), this can lead to an egg
cell or sperm with two X's, two Y's, or with neither an X or a Y. Fertilization involving
one of these abnormal gametes results in a zygote with either an extra or missing
chromosome (aneuploidy). Aneuploidy causes various clinical syndromes. Sex chromosome aneuploidies include Klinefelter
syndrome (XXY), Turner syndrome (XO), triple-X (XXX), and the XYY karyotype. Individuals with Klinefelter syndrome have 47
chromosomes, are sterile, and may show some degree of mental retardation. Individuals with Turner syndrome (XO) are sterile and
have underdeveloped genital structures.
Humans can tolerate sex chromosome aneuploidies better than other aneuploidies because of dosage compensation. Dosage
compensation refers to the way the system inactivates one X chromosome in normal females. As a result of dosage compensation, the
expression of X-linked genes is equivalent in normal females with two X chromosomes and normal males with one X chromosome.
Chromosomes Aneuploidy: Autosomes
Most autosomal aneuploidies have devastating effects on
the fetus and end in miscarriage. A common syndrome
resulting from nondisjunction of autosomes
(chromosomes other than sex chromosomes) in which
many children survive is Down syndrome. Individuals
with Down syndrome often have 47 chromosomes
(instead of the usual 46). Most are trisomic for
chromosome 21, meaning that they have three copies of
that chromosome. Extra copies of autosomes cause
genetic imbalance. In Down syndrome, this results in
abnormal physical development (face, eyelids, tongue,
hands) and, frequently, mental retardation.
Because Down syndrome is much more common in
children of older mothers, at-risk pregnant women
regularly choose amniocentesis and karyotyping of the
fetal fluid to determine whether the fetus has a normal
karyotype or an extra chromosome 21.
Chromosomes Structural Abnormalities
Human disease also results from abnormal
chromosomal structure due to translocations,
deletions, and fragile sites. In one type of
translocation, part of a chromosome breaks off and
reattaches to a different chromosome (which results in
extra copies of the translocated genes). In about 4% of
Down syndrome sufferers, an extra piece of
chromosome 21 is translocated onto a larger
chromosome, such as chromosome 14.
Sometimes chromosomes break but fail to rejoin.
Such breaks result in deletions of base pairs. Large
deletions are lethal, and small deletions cause several
recognizable disorders.
Fragile sites occur on various autosomal and sex
chromosomes. One, on the tip of the X chromosome, results in fragile X syndrome. This causes mild retardation in about 80% of boys
and 35% of girls.
Single Gene Mutations
Many more human diseases result from single gene mutations than from chromosome
abnormalities. These include sickle-cell anemia, cystic fibrosis, Huntington disease,
phenylketonuria (PKU), and alkaptonuria. These disorders, referred to as inborn errors
of metabolism, result from mutations in a single gene, which causes the absence of, or
incorrect form of, the protein for which that gene codes.
These diseases usually are inherited as autosomal recessive traits. The heterozygous
parents each have one normal copy of the gene and one mutated, nonfunctional copy.
In the heterozygote, the cell's normal gene compensates by making more protein. The
homozygous recessive individuals, however, exhibit the disorder because both gene
copies are nonfunctional and the correct gene product is missing.
Sex linkage
Among the 23 pairs of chromosomes in human cells, one pair is the sex chromosomes. The remaining 22 pairs of chromosomes are
referred to as autosomes. The sex chromosomes determine the sex of humans. There are two types of sex chromosomes: The X
chromosome and the Y chromosome. Females have two X chromosomes and males have an X and Y chromosome. Typically, the
female chromosome pattern is designated XX, while the male chromosome pattern is designated XY. Thus, the genotype of the
human male would be 44XY, while the genotype of the human female would be 44XX (where 44 represents the autosomes).
In humans, the Y chromosome is much shorter than the X chromosome. Because of this shortened size, a number of sex-linked
conditions occur. When a gene occurs on the other X chromosome, the other gene of the pair probably occurs on the other X
chromosome. Therefore, a female usually has two genes for a characteristic. In contrast, when a gene occurs on an X chromosome in
a male, there is usually no other gene present on the short Y chromosome. Therefore, in the male, whatever gene is present on the X
chromosome will be expressed.
An example of a sex-linked trait is colorblindness. The gene for colorblindness is found on the X chromosome. A woman is rarely
colorblind because she usually has a dominant gene for normal vision on one of her X chromosomes. However, a male has a
shortened Y chromosome; therefore, he has no gene to offset a gene for colorblindness on the X chromosome. As a result, the gene
for colorblindness expresses itself in the male.
Answer the following based on your reading:
1. Name a disorder caused by an abnormality in chromosome number, a gene mutation, and a chromosome structure
abnormality.
2. Name a sex-linked chromosome abnormality and a sex-linked gene disorder. How do they differ?
3. What is dosage compensation?
4. Why are sex-linked diseases more common in males?
5. Does the age of the mother increase the chances of having offspring with a genetic disease? Explain.
6. What is an aneuploidy?
7. Explain how a non-disjunction affects the offspring.
8. During which phase(s) of meiosis do you think a non-disjunction would occur? Explain.
9. What are the symptoms of Down syndrome?
10. What are the two ways in which you can get Down syndrome?
2. Making Pedigrees:
Date: _____________________
A. Draw a pedigree from the following information. Jack and Jill went up a hill and came down with three children two boys
and one girl. Jack has two brothers and four sisters. His oldest sister is married with one boy. Jack’s parents are Jake and
Jane. Jill’s parents are John and Jen. Jill is an only child.
B. Draw a pedigree from the following information. Widow’s peaks run in Joe’s family. Joe has a widow’s peak however is
two sisters do not. Joe’s dad Paul is normal but his two sisters have a widow’s peak. Joe’s mother Sara has a widow’s peak as
well as Sara’s sister Jane. Sara’s brother Mark does not have one. Jane married Pete. Pete does not have a widow’s peak but
their three children-two boys and one girl all do.
Questions for pedigree B:
1. How many boys are there in your pedigree?
2. How many girls are there in your pedigree?
3. How many union lines are there in your pedigree?
4. How many generations are there in your pedigree?
5. How many people have a widow’s peak?
6. How many are do not have a widows peak?
C. Use the following information to draw a pedigree for this family: Peter married Gissel and they have 4 kids-3 boys and 1
girl. Peter’s oldest son John is married to Maria and they have 2 kids, both girls. Peter has 1 brothers and 2 sisters all of
which are married. Peter’s brother has one daughter, his older sister Sharon has two kids, a boy and a girl and his younger
sister doesn’t have any children yet. Sharon’s daughter is married with two girls of her own. Peter’s parents are Leslie and
Josh. Josh has two older brothers. Gissel has one married sister with three boys. Gissel’s parent, Camron and Jennifer were
both only children.
Questions for pedigree C:
1. How many boys are there in your pedigree?
2. How many girls are there in your pedigree?
3. How many union lines are there in your pedigree?
4. How many generations are there in your pedigree?
3 .Interpreting Information in a Pedigree:
Date: ______________________
Part 1: Copy the pedigree below for hemophilia, a sex linked disorder, on your paper. In the pedigree a square represents a
male. A darkened square represents a male with the hemophilia. A circle represents a female. A darkened circle represents a
female with hemophilia.
P1
F1
F2
F3
Label all individuals with XAXA, XAXa, XAX?, XaXa, XAY, or XaY for the sex linked pedigree above.
How many males are there? How many have hemophilia? How many don’t?
How many females are there? How many have hemophilia? How many don’t?
A union is indicated by a line connecting a circle to a square. How many union are there?
The line perpendicular to the marriage line indicates the children the couple has had. How many children did the couple
in the P1 generation have? How many did the first couple in the F2 generation have?
6. How many generations are there?
7. Which sex usually inherits a sex-linked condition?
8. How many genotypes are possible in a sex linked pedigree? What are they?
9. What is the genotype of the female in the first generation?
Part 2: Organization is often the key to solving a problem. Tracing the hereditary characteristics over many generations can
be especially confusing unless the information is well organized. In this activity, you will learn how to organize hereditary
information, making it much easier to analyze.
1.
2.
3.
4.
5.
Part 2: Copy the pedigree on your own paper. The pedigree below traces the dimple trait through three generations of a
family. Blackened symbols represent people with dimples. Circles represent females and squares represent males.
P1
F1
F2
1.
2.
Label the genotype of all the individuals in the pedigree as DD, Dd, D?, or dd.
From the following passage give a name to all the people in the pedigree: Although Jane and Joe Smith have dimples, their
daughter, Clarissa, does not. Joe’s dad has dimples, but his mother, and his sister, Grace, do not. Jane’s dad, Mr.
Renaldo, her brother, Jorge, and her sister Emily, do not have dimples, but her mother does.
Part 3: Make a pedigree based on the following passage about freckles.
Andy, Penny, and Delbert have freckles, but their mother, Mrs. Cummins, does not. Mrs. Cummins’s sister, Mrs. Giordano
has freckles, but her parents, Mr. and Mrs. Lutz, do not. Mrs. Giordano’s children, Deidra and Darlene Giordano are
freckled, but their sister, Dixie, like her father, is not freckled
4. Labeling disorders:
Date: ______________________
Copy, label and determine the pattern of inheritance for the following pedigrees.
1.
2.
3.
4.
5.
5. Human Pedigrees: Applied Genetics
Date: ___________________________
By studying a human pedigree, you can determine whether a trait is dominant, recessive or sex linked. You are a genetic
counselor and your job is to:
1. Determine how the genetic disorder is passed on.
2. Label the genotype of every person in every generation (AA, A?, Aa, or aa) to the left of the person. If sex linked use
XAXA, XAXa, XAX?, XaXa, XAY, or XaY
Part 1:
Use the following key for pedigrees 1-3.
Male with the trait.
Male without the trait
Female with the trait
Female with out the trait
1.
P1
F1
F2
F3
Is the trait for attached earlobes vs. free earlobes, dominant or recessive? How do you know?
2.
P1
F1
F2
F3
Is the trait for tongue rolling dominant or recessive? How do you know?
3.
P1
F1
F2
F3
How is the trait for colorblindness passed on?
Part 2: Duchenne muscular dystrophy is a deadly disorder in which the muscles grow progressively weaker. The disease is
caused by a recessive gene on the X chromosome. The pedigree below illustrates the inheritance of this gene. Use the pedigree
to answer the questions that follow.
A
B
Key:
Normal female
C
D
E
F
Normal male
Carrier female
G
H
I
J
K
Affected
female
1.
2.
3.
4.
5.
6.
7.
Label the genotype of every person in the pedigree (A-K).
Is Duchenne muscular dystrophy more likely to occur in males or in females? Explain.
Individual H is a female with the disorder. Explain how she inherited this disease.
Affected
Individual K has this disorder, yet his father did not. Explain how this is genetically possible.
Individual G does not have the disease, yet his mother was a carrier and his father has the disease. Explain
how this is possible.
Why don’t you see any male carriers?
Why is the genotype of the father unimportant when investigating sex-linked traits inherited by male
offspring?
male
6. Genetic disorders:
Date: ____________________
Label your paper 1-16. Look at the table below and list the letters from each column that match the disordered mentioned
some answers from the special features column may be used more then once for a given disorder:
Disorder:
Symptoms:
Mode of inheritance:
Special features:
1. Color-blindness
A. Individuals have trouble
A. Autosomal
A. Homozygous dominant
2. Jacob’s syndrome
clotting their blood.
Dominant
individuals are never born.
3. Tay sachs disease
B. Autosomal
B. 45XO
B. Males only. They tend to be
4. Edward’s syndrome
Recessive
C. High incidence in the
somewhat taller than the average
5. Cystic fibrosis
C. Sex-linked
Ashkenazi Jews of central
male and have low mental ability
6. Sickle cell anemia
Recessive
Europe
due to an extra Y chromosome.
7. Down syndrome
D. Chromosomal
D. Trisomy 21
C. Individuals are born with too
8. Albinism
E. Shows heterozygous
many digits.
9. Turner’s syndrome
superiority.
D. Usually in males, they have
10.Polydactyl
F. 48XXXY
trouble distinguishing different
11. Meta-females
G. 47XXT13
colors.
12. Huntington’s disease
H. 47XXX
E. Animals or plants are missing
13. Achondroplasia dwarfism
I. Monosomy X
coloring pigments and are
14. Klinefelter syndrome
J. Seem to be a high
partially or completely white.
15. Hemophilia
incidence of these males in
F. Males only. They have 2 or
prison.
more X chromosomes.
K. The most common lethal
G. Young children accumulate
genetic disorder in the United
lipids on their brains.
States. Is known as a
H. Individuals are missing the
Caucasian disorder.
genes for proper growth
L. Trisomy 18
hormones and are abnormally
M. 47XYT18
short.
N. Is most common in the
I. Most infants live less than a
black population.
th
year due to an extra 13
O. Trisomy X
chromosome.
P. Heterozygous individuals
J. Red blood cells are not shaped
are immune to malaria.
right and carry less oxygen.
Q. 47XXY
K. Brain deterioration occurs
R. The only viable human
around 35 to 45.
monosomy
L. Females only, do not develop
secondary sex characteristics.
M. Individuals have a short
stature, stubby fingers and toes,
heart defects, susceptibility to
respiratory infections and mental
retardation due to an extra 21st
chromosome.
N. Thick mucous accumulates in
the lungs and other organs.
O. Most infants live less than a
year due to an extra 18th
chromosome.
P. Females only. They have
limited fertility and may be
mentally retarded due to an extra
X chromosome.
Part 2: For the following crosses give me the probability of having an affected male, an affected female, a normal male and a
normal female.
Parental description
Affected
Affected
Normal Normal
male
female
male
female
1. A female with cystic fibrosis mates with a male that is a carrier.
2. A male that is red-green colorblind mates with a carrier female.
3. Two dwarfs mate.
4. A male that is homozygous dominant for Huntington’s disease mates
with a normal female.
5. A female with hemophilia mates with a normal male.
6. Two heterozygous individuals for the Tay-Sachs allele.
7. A male with hemophilia mates with a carrier female.
8. Two albinos mate.
9. Two normal sized individuals mate, what is the chance they will have a
dwarf?
10. Two individuals that are heterozygous for Polydactyly
Part 3: Label the following karyotypes and tell me the phenotype.