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1st Midterm Exam
Biology 102
Fall quarter 2002
Name:_____________________________________________
Discussion Section:__________________________________
TA Name:_________________________________________
1. If a plant of the genotype AaBbCcDd is selfed and the genes assort independently, how many
different phenotypes will be found among the progeny? (Assume a simple dominance for each pair
of alleles)
A) 64
B) 4
C) 8
D) 16
E) 32
2. A couple are both heterozygous for two autosomal recessive diseases: cystic fibrosis (CF) and
phenylketonuria (PKU). What is the probability of their first child having either CF or PKU? (Only
one or another, but not two diseases together. Assume no linkage)
A) 1
B) 3/16
C) 1/4
D) 3/8
E) 1/16
3. In the above problem, what is the probability of their first child having both CF and PKU?
A) 1
B) 3/16
C) 1/4
D) 3/8
E) 1/16
4. What proportion of cells in a pool of human sperm will have centromeres all of which are from
the man's father?
A) All of them
B) 1/2
C) (1/2)23
D) (46)1/2
E) (23)1/2
5. Drosophila flies have a diploid chromosome number 8 (2n=8). How many centromeres are present
in each daughter cell after the first division of meiosis?
A) 4
B) 8
C) 16
D) 32
E) 2
6. Two gene pairs interact to influence the shape of the comb in chickens. The genes for rose comb
(R) and pea comb (P) together produce walnut comb. The fully homozygous condition (rrpp)
produces the single comb. Assume that a rose-comb chicken is crossed with a walnut-comb chicken
and the following offspring are produced: 14 walnut, 16 rose, 5 pea, 4 single. What are the most
probable genotypes of the parents?
A) Rrpp x RrPp
B) RrPp x RrPp
C) RrPp x rrPp
D) RrPp x rrpp
E) RRPP x rrpp
7. Recessive allele of one gene prevents the phenotypic expression of alleles of another genes. What
best describes this phenomenon?
A) incomplete dominance
B) complementation
C) epistasis
D) low expressivity
E) incomplete penetrance
8. A plant of genotype CCdd is crossed to ccDD and an F1 testcrossed to ccdd. If you observe that
the percentage of CcDd and ccdd classes together is 50%, you correctly conclude that:
A) there is linkage at 50 m.u.
B) there is linkage at 25 m.u.
C) there is no linkage
D) the alleles segregate equally
E) the Earth is flat
9. Assume that a chi-square test was conducted to test the goodness of the data fit to a 9:3:3:1 ratio
and a chi-square value of 10.62 was obtained (the table of chi-square probabilities is on the last
page). You then determine that
A) 0.01<p<0.025, and you accept the null hypothesis
B) 0.025<p<0.05, and you reject the null hypothesis
C) 0.05<p<0.1, and you accept the null hypothesis
D) 0.1<p<0.5, and you accept the null hypothesis
E) 0.01<p<0.025, and you reject the null hypothesis
10. In Drosophila, the two genes w and sn are X-linked and located at 20 m.u. apart. A female fly of
the genotype w+ sn+ / w sn is crossed to a male from a wild type line. What percent of the male
progeny will be of the w+ sn phenotype?
A) 0
B) 10
C) 20
D) 40
E) 5
11. Mendel’s first and second laws state that:
A) during gamete formation the ploidy gets reduced due to equal segregation of alleles
B) during gamete formation alleles segregate equally and some loci assort
independently
C) in diploid organisms all loci always segregate equally and assort independently
D) alleles segregation occurs during the first division of meiosis
E) in haploid organisms there is a diploid stage when meiosis occurs
12. The A, B and C loci are linked in the order written and there are 10 m. u. between A and B, and
20 m. u. between B and C. If a plant ABC / abc is testcrossed, what proportion of progeny will be
abc / abc (assuming there is no interference)?
A) 0.10
B) 0.20
C) 0.18
D) 0.36
E) 0.72
13. A couple with normal vision have a daughter with red-green color blindness (rare X-linked
recessive). The man sues his wife for divorce on the grounds of infidelity saying it is impossible that
he fathered the child. The man's lawyers call you in as a genetics expert. You tell them that most
likely
A) he is a father, since this is a recessive trait
B) he is a father, since this is a mother-to-daughter inheritance
C) he is a father, since this is a trait which often appears spontaneously
D) he is not a father, since otherwise he also must have this trait
E) he is not a father, since men do not transmit sex chromosomes to daughters
14. A pure-breeding plant with red petals is crossed to a pure-breeding plant with white petals, the F1
plants are all red. However, the F2 produced by selfing of F1 plants, shows 9/16 red, 1/16 white and
6/16 pink. The pink phenotype is most likely determined by
A) complementation of alleles of the two genes
B) incomplete penetrance
C) recessive epistasis
D) dominant epistasis
E) the presence of a dominant allele at either one of the two loci
15. The process that occurs in meiosis II but not in meiosis I is
A) centromere division
B) metaphase alignment
C) spindle formation
D) nondisjunction of chromosomes
E) movement of chromosomes in opposite directions
16. Three-point testcross is
A) any cross in which three loci are involved
B) a cross which involves two triple recessive homozygotes
C) any cross in which eight classes are produced
D) a cross which involves three heterozygotes
E) a cross which involves a triple recessive homozygote and a triple heterozygote
17. The following pedigree presents a rare hereditary condition involving involuntary movement of
the eyeballs (not to be confused with ogling). What is the most likely mode of inheritance of this
disease?
A) Autosomal dominant
B) Autosomal recessive
C) X-linked dominant
D) X-linked recessive
E) Y-linked
18. Out of the progeny of a three-point testcross there were 16 double recombinants whereas 80 had
been expected on the basis of no interference. The interference must have been
A) 16%
B) 32%
C) not enough data (total progeny number is unknown)
D) 64%
E) 80%
19. You perform a cross of an AabbCc individual with an aabbCc individual and verify a resulting
genotypic ratio with the chi-square analysis. How many degrees of freedom are there?
A) 6
B) 5
C) 4
D) 3
E) 2
20. In the fruit fly, a spineless (sp, no wing bristles) female fly is mated to a male which is claret (cl,
dark eyes) and hairless (h, no bristles on thorax). Phenotypically wild type F1 female progeny were
mated to fully homozygous (mutant) males and the following progeny (1000 total) were observed:
spineless
321
wild
38
claret, spineless
130
claret
18
claret, hairless
309
hairless, claret, spineless
32
hairless
140
hairless, spineless
12
What are the genotypes of the parents used in making the F1 (with correct gene order)?
A) cl h +/cl h + and + + sp/+ + sp
B) h cl +/h cl + and + + sp/+ + sp
C) + cl h/+ cl h and sp + +/sp + +
D) cl h sp/cl h sp and + + +/+ + +
E) cl h +/+ + sp and cl h +/+ + sp
21. In the previous problem, what are the map distances between the adjacent loci
A) 27 m.u. and 7 m.u.
B) 10 m.u. and 30 m.u.
C) 16.8 m.u. and 17.2 m.u.
D) 32.1 m.u. and 30.8 m.u.
E) 5 m.u. and 4.4 m.u.
22. In the two previous problems, is there evidence for interference?
A) Observed DCO progeny is close to expected, there is interference
B) Observed DCO progeny is close to expected, no evidence for interference
C) Observed DCO progeny is much less than expected, strong interference
D) Observed DCO is higher than expected, do not know how to interpret
E) No DCO progeny is observed, absurd question
23. Given a map
X
Y
Z
10 m. u.
10 m. u.
and the interference of 20%, how many double crossover progeny would you observe in the total
number of 1,000?
A) 92
B) 20
C) 2
D) 80
E) 8
24. In the previous problem, how many progeny is due to a single cross-over between the loci X and
Y?
A) 92
B) 80
C) 90
D) 20
E) 100
25. In a four-point testcross, the numbers of genotypic and phenotypic progeny classes are,
respectively,
A) 24 and 34
B) 34 and 24
C) 34 and 34
D) 24 and 24
E) four-point cross?! there is no way we would know.