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-1Bio 309F
First Preliminary Examination
February 18, 2003
Name_____________________________________
I. Short Answers: (5 points each, 30 points total)
1. Cystic fibrosis is a Mendelian trait; obesity is a multifactoral trait. How do the causes of these two
traits differ?
2. A normal couple with a cystic fibrosis child would like to have three more children. They consult
with a genetic counselor who informs them that they are both carriers of cystic fibrosis and that each
future child has a 1 in 4 chance of also inheriting cystic fibrosis. The parents leave the session relieved
since they already have a cystic fibrosis child, they reason that the next three will be healthy. How are
they wrong?
3. How does meiosis differ from mitosis?
-24. What are teratogens, and why do they tend to produce more severe congenital deformities in an
embryo than in a fetus?
5. How was Mendel able to derive the two laws of inheritance (dominance versus recessive and
segregation of alleles) without having any knowledge about chromosomes, loci, or alleles?
6. Albino or lack of pigment in the skin is an autosomal recessive trait. An albino couple have a child
that is normal pigmented. How can this happen?
-3II. Multiple Choice (2 points each, 50 points total)
1. A somatic cell from a normal human will contain a total of ________ chromosomes
A. 22 chromosomes
B. 23 chromosomes
C. 44 chromosomes
D. 46 chromosomes
E. none of the above
2. A somatic cell from a normal human will contain _________ autosomal chromosomes
A. 22 chromosomes
B. 23 chromosomes
C. 44 chromosomes
D. 46 chromosomes
E. none of the above
3. A human gamete (egg or sperm) will contain a total of _________ chromosomes
A. 22 chromosomes
B. 23 chromosomes
C. 44 chromosomes
D. 46 chromosomes
E. none of the above
4. 100 primary speratocytes undergoing meiosis would give rise to _______spermatids (sperm)
A. 50
B. 100
C. 200
D. 300
E. 400
5. 100 primary oocytes undergoing meiosis would give rise to _______ovids (egg)
A. 50
B. 100
C. 200
D. 300
E. 400
Note: Consider the following information for questions 6-9. Cystic fibrosis is inheritated as an
autosomal recessive trait: C = normal, c = cystic fibrosis trait
6. A normal couple have a cystic fibrosis child. What are the genotypes of the parents
A. CC X CC
B. Cc X CC
C. Cc X Cc
D. Cc X cc
E. cc X cc
-47. The couple in question 6 are expecting another child. What is the probability (chance) that this
expectant child will inheritance cystic fibrosis?
A. 3/4
B. 1/2
C. 1/4
D. 2/3
E. 1/3
8. What is the chance that this expectant child (from question 7 above) will be normal (not have cystic
fibrosis)?
A. 3/4
B. 1/2
C. 1/4
D. 2/3
E. 1/3
9. The expectant child (from questions 6 & 7 above) finally arrives and is normal. What is the
probability that this child is a carrier of the cystic fibrosis trait?
A. 3/4
B. 1/2
C. 1/4
D. 1/3
E. 2/3
Note: Consider the following additional information for questions 10-13. A different couple are normal
for the cystic fibrosis trait have brown eyes. Brown eyes are inherited as an autosomal dominant trait,
blue eyes are inherited as a recessive trait. B = brown, b = blue
10. The couple have a child who has cystic fibrosis and blue eyes. What are the genotypes of the
parents?
A. CCBB X CCBB
B. CcBb X CCBB
C. Ccbb X Ccbb
D. CcBb X CcBb
E. CcBb X Ccbb
11. The couple in question #10 are expecting another child. They would like to know the chance that
the expected child will have cystic fibrosis and blue eyes?
A. 1/4
B. 3/4
C. 9/16
D. 3/16
E. 1/16
-512. What is the chance that the expected child from question #10 will be phenotypically like the parents,
normal for the cystic fibrosis trait and have brown eyes?
A. 1/4
B. 3/4
C. 9/16
D. 3/16
E. 1/16
13. The child from question #10 is finally born and is normal for the cystic fibrosis trait and has brown
eyes. What is the chance that this normal child is a carrier for both the cystic fibrosis trait and blue
eyes?
A. 9/16
B. 3/16
C. 1/16
D. 2/9
E. 4/9
Note: Consider the following information for questions 14-16. Color blindness is inherited as a sex-(X
chromosome)-linked recessive trait C = normal and c = color blind.
14. The first child for a couple who are normal for the colorblind trait have a son that is colorblind.
What are the genotypes of the parents?
Mother
Father
A.
Cc
Cc
B.
Cc
Cy
C.
Cc
cy
D.
cc
Cy
E.
cc
cy
15. The couple in question # 14 are expecting another child. They would like to know the chance that
this expected child will be a colorblind male?
A. 1/4
B. 1/2
C. 3/4
D. 100 % chance
E. 0% (No chance)
16. The expected child is finally born and is a daughter. What is the change that this daughter is
colorblind?
A. 1/4
B. 1/2
C. 3/4
D. 100 % chance
E. 0% (No chance)
-617. A normal female who is a carrier of the colorblind trait is married to a colorblind man. This couple
has a daughter. What is the chance that this daughter is colorblind?
A. 1/4
B. 1/2
C. 3/4
D. 100 % chance
E. 0% (No chance)
18. Analyses of a stained chromosomal preparation revealed a cross-like chromosomal configuration.
The cross-configuration is indicative of a _____________.
A. inversion
B. deletion
C. duplication
D. reciprical translocation
E. gene mutation
19. Analyses of chromosomes in white blood cells from a new born revealed 47 chromosomes in each
cell. This chromosomal aberation is referred to as:
A. Aneuploidy
B. Euploidy
C. Polyploidy
D. Triploidy
E. Monosomy
20. Down's Syndrome can be due to:
A. trisomy 21
B. somatic mosaic with cells containing 2N chromosomes and other cells with 2N +1(21)
C. cells containing two 21 chromosomes + translocated fragment of chromosome 21
D. A and B are correct
E. A, B, and C are correct
21. Nuclei of white blood cells from an individual show a single Barr body. The white blood cells
could have come from
A. normal female
B. normal male
C. Klinefelter male
D. Turner syndrome
E. A and C are correct
F. A and D are correct
-722. Nuclei of white blood cells from an individual do not show any Barr bodies. The white blood cells
could have come from
A. normal female
B. normal male
C. Klinefelter male
D. Turner syndrome
E. A and C are correct
F. B and D are correct
23. In meiosis, the occurrence of an N + 1 gamete is most likely due to:
A. chromosomal mutation
B. chromosomal rearrangement
C. chromosomal polarity
D. non-disjunction
E. absence of crossing-over
23. An individual with the testicular feminization phenotype will have________sex chromosomes
A. XX
B. XXY
C. XY
D. YY
E. X0
24. The autosomal dominant disease familial hypercholesterolemia is caused by _____________
A. Too many LDL cell surface receptors
B. Too many LDL cytosolic receptors
C. reduced numbers to absence of LDL cell surface receptors
D. reduced numbers to absence of LDL cytosolic receptors
E. none of the above
25. The concordance values of blood types in identical twins are:
A. 0%
B. 33%
C. 54%
D. 67%,
E. 100%
-8-
III. Matching (1.5 points each, 20 points total)
______1.
Allele
a. cells that can differentiate into different cell types
______2.
Karyotype
b. specific genetic constitution of an individual
______3.
Autosome
c. monohybrid genotypic ratio
______4.
Genotype
d. exchange of DNA between homologous chromosomes
______5.
Phenotype
e. failure of dominant phenotype to be expressed in F1
______6.
Stem cell
f. expression of both alleles eqally in an individual
______7.
9:3:3:1 ratio
g. monohybrid test cross ratio
______8.
1:2:1 ratio
h. one of two forms of a gene in an individual
______9.
1:1 ratio
i. 2N
_____10.
present
Incomplete dominance
_____11.
Codominance
k. genetic controlled visible traits of an individual
_____12.
Penetrance
l. non-sex chromosomes
_____13.
Diploid
_____14.
Haploid
n dihybrid phenotypic ratio
_____15.
Crossing Over
o
j. chance phenotype will appear when gene is
m N
chromosome complement of a cell or person
Bonus question (3 points)
When you see a calico cat, you instantly know that the cat is a female. What is the explanation for
knowing that calico cats are females?