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Biol 102
Midterm I
version 1
Midterm I
Biology 102, Fall 2005
Name: _______________________________
Discussion Section: _____________________
TA’s Name: ___________________________
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Biol 102
Midterm I
version 1
1. Mendel’s laws state that
a) alleles segregate equally and pairs of alleles assort independently
b) alleles segregate independently and pairs of alleles assort equally
c) a monohybrid cross demonstrates a phenotypic 3:1 ratio
d) a dihybrid cross demonstrates a phenotypic 9:3:3:1 ratio
e) intrachromosomal recombination produces parental progeny at 50%
2. During a three-point testcross in Drosophila
a) one parent is recessive homozygote
b) a heterozygous female is crossed with a homozygous male
c) eight classes of progeny are produced
d) all of the above
e) none of the above
3. Complementation in a dihybrid cross occurs when
a) a 9:7 ration is seen in F2
b) two pure-breeding parents with a mutant phenotype produce a wild type F1
progeny
c) a wild type phenotype is produced in F1 only when dominant alleles of both
genes are present
d) all of the above
e) only two of the answers above are correct
4. Epistasis
a) a dominant allele of one gene prevents the phenotypic expression of alleles of
another gene
b) two recessive alleles of one gene prevent the phenotypic expression of alleles
of another gene
c) phenotype is determined by a dominant allele of one gene
d) a lethal allele is responsible for a 9:4:3 ratio in F2
e) only two of the answers above are correct
5. The average pea pod contains about 7 peas. The round shape of peas is determined by a
dominant allele (R). If heterozygous round pea plants (R/r) are self-fertilized, what proportion of
pods in the F1 plants will have all round peas? (shape of any single pea in the pod is determined
independently from its neighbors)
a) ¾
b) ¼
c) 13.5%
d) 50%
e) 100%
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Biol 102
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6. A triple heterozygous Drosophila female of the wild type phenotype (gray body, red eyes,
normal wings) is test-crossed to male with black body (b), purple eyes (pr) and vestigial wings
(vg). The following eight phenotypic classes of progeny are obtained:
+++
411
+ + vg
61
+ pr +
2
+ pr vg
30
b++
28
b + vg
1
b pr +
60
b pr vg
412
The correct gene order and allele configuration on the chromosome of the female is:
a) vg pr b / + + +
b) vg b pr / pr b vg
c) + + + / + + +
d) b pr vg / b pr vg
e) pr b vg / + + +
7. In the previous problem, the distances between the loci are:
a) 12.0 m.u. and 5.8 m.u.
b) 12.3 m.u. and 6.1 m.u.
c) 6.0 m.u. and 3.0 m..u
d) 41.1 m.u. and 41.2 m.u.
e) impossible to determine
8. In the previous two problems, is there a DCO interference?
a) no
b) yes, 40%
c) yes, 60%
d) yes, 7.5%
e) yes, it is always there
9. A diploid cell with 2n = 26 in early metaphase I of meiosis contains:
a) 26 centromeres, 26 chromosomes and 52 chromatids
b) 26 centromeres, 52 chromosomes and 52 chromatids
c) 26 centromeres, 26 chromosomes and 26 chromatids
d) 52 centromeres, 52 chromosomes and 52 chromatids
e) 13 centromeres, 26 chromosomes and 52 chromatids
10. When two loci demonstrate 50% frequency of recombination, it can be concluded that these
loci are:
a) linked at 50 m.u. distance
b) linked at a distance exceeding 50 m.u.
c) localized on different chromosomes
d) assort independently
e) any of the above
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Biol 102
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11. Two homologous chromosomes generally are:
a) identical copies of each other
b) completely dissimilar from each other
c) known to contain different alleles of the same set of genes
d) found within the same haploid set of chromosomes
e) shown to assort independently in meiosis
12. If the organism contains 16 tetrads (synapsed pairs of homologs) in Prophase I, the diploid
number of chromosomes (2n) in this organism is:
a) 8
b) 32
c) 16
d) 64
e) 48
13. In the problem above, how many chromatids are present in each daughter cell after
completion of meiosis I?
a) 8
b) 32
c) 16
d) 64
e) 48
14. In a plant, two autosomal loci Aand B are linked at 20 m.u. What proportion of the progeny
with a phenotype AB will be obtained if a double heterozygous plant (aB/Ab) is testcrossed:
a) 5%
b) 10%
c) 20%
d) 50%
e) 3/16
15. A couple, in which the husband has hemophilia and color-blindness and the wife (as well as
all her known relatives) are not affected, had a daughter who married an unaffected man.
Assuming that the genes responsible for hemophilia and color blindness are X-linked at 10 m.u.,
the probability of the first child of the younger couple being a boy without hemophilia or colorblindness is:
a) 0.45
b) 0.5
c) 0.1
d) 0.225
e) 0.2
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Biol 102
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16. The gene for yellow body color in Drosophila is recessive and X-linked. Its dominant allele
produces normal gray body color. The progeny expected from the cross of a heterozygous female
to a yellow male will show:
a) for both males and females, half yellow and half gray
b) all females yellow, all males gray
c) all females gray, half males yellow
d) half females yellow, all males gray
e) all females gray, all males yellow
17. In a dihybrid test-cross, a progeny of four phenotypic classes were obtained:
AB
68
Ab
65
aB
55
ab
60
Is this result consistent with the hypothesis of independent assortment of the two pairs of alleles
in question ?
a) yes, 0.5 < P < 0.9
b) yes, 0.1 < P < 0.5
c) yes, 0.05 < P < 0.1
d) no, 0.025 < P < 0.05
e) no, 0.01 < P < 0.025
18. In diploid organisms one set of homologous chromosomes is inherited from a father and
another set is from a mother. If 2n = x, what is the probability that any randomly picked gamete
will contain all its chromosomes from one parent?
a) ½ n
b) ½
c) ½ n-1
d) ½ n+1
e) ½ 2n
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19. In a plant, 2n = 4, with one long and short pair of chromosomes. A researcher investigates
cell division in a double heterozygote (A/a; B/b) using a microscope. Suppose that she/he can
somehow make each allele “visible” on the corresponding chromosome. Two cells, apparently in
Anaphase, are currently viewed by the researcher:
A
A
1
A
b
b
B
B
B
2
b
a
a
a
The researcher correctly concludes that:
a) cell 1 is in mitosis, cell 2 is in meiosis
b) cell 1 is in meiosis II, cell 2 is in meiosis I
c) cell 1 is in meiosis I, cell 2 is in meiosis II
d) cell 1 is impossible or aberrant, cell 2 is in normal meiosis
e) cell 1 is in normal mitosis, cell 2 is aberrant
20. Normal hearing in humans depends upon the presence of at least one dominant allele from
each of two pairs, D and E. If you examined the collective progeny of many
D/d; E/e x D/d; E/e marriages, what phenotypic ratio would be expected?
a) all deaf
b) 13 normal : 3 deaf
c) all normal
d) 13 deaf : 3 normal
e) 9 normal : 7 deaf
21. Given a map A ___ 5 m.u. ___ B ___ 10 m.u. ___ C, and interference of 40%, predict the
frequency of double crossover progeny observed in a testcross of a triple heterozygote for these
loci.
a) 3 x 10-3
b) 5 x 10-3
c) 10-3
d) 4 x 10-2
e) 6 x 10-2
22. In the problem above, what is the frequency of the progeny produced by a single crossover
between the loci A and B?
a) 0.155
b) 0.1
c) 0.095
d) 0.047
e) 0.05
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Biol 102
Midterm I
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23. The following pedigree illustrates inheritance of a rare genetic trait in humans. What is the
most likely mode of inheritance of this trait?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked dominant
d) X-linked recessive
e) Y-linked
24. In the previous question, the person indicated with an arrow wants to know what are the
chances that she will have a child with the trait. Assuming that her husband does not have an
allele for this trait, the chances are:
a) 0
b) 1/16
c) 1/8
d) 1/4
e) 1/2
25. In a cross A/a; B/B; C/c; D/D; e/e to A/a; B/b; c/c; D/d; e/e, how many phenotypic classes
are produced and in which ratio?
a) four classes; 9:3:3:1
b) four classes; 3:3:1:1
c) five classes; 27:3:9:1:9:1:3:1
d) six classes; 81:27:9:3:27:9:3:1:27:9:3:1:9:3:3:1
e) 10 classes (25); the ratio is very complex
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