Part I 1. The cross AaBb x AaBb is called a
a. dihybrid cross; b. backcross; c. reciprocal cross; d. testcross; e. monohybrid cross
2. Assuming codominance for both genes, what is the phenotypic ratio of the offspring of the
cross AaBb x AaBb?
a. 1:2:1:2:4:2:1:2:1; b. 9:4:1; c. 9:3:3:1; d. 3:6:3:1:2:1; e. 1:2:1
3. The cross AaBb x aabb is called a
a. dihybrid cross; b. backcross; c. reciprocal cross; d. testcross; e. monohybrid cross
4. Assuming complete dominance, what is the phenotypic ratio of the offspring of the cross
AaBb x aabb?
a. 1:1; b. 3:1; c. 1:1:1:1; d. 9:3:3:1; e. 1:2:1
5. Corn has a color gene and a height gene with the following phenotypes: CC and Cc, purple;
cc, white; TT, tall; Tt, medium; tt, dwarf. If a dihybrid is self-fertilized, what is the resulting
phenotypic ratio?
a. 1:2:1:2:4:2:1:2:1; b. 2:3:6:3:2; c. 3:3:3:3:3:1; d. 3:6:3:1:2:1; e. 3:1
6. Mendel's work on the rules of inherited traits was not appreciated until it was rediscovered in
1900 because
a. his work lacked scientific controls;
b. he never published his work.
c. there was no known physical basis for Mendel's "gene" concept at the time.
d. it was found that Mendel cheated.
e. none of these choices
7. Full pod shape (F) is dominant to constricted pod shape (f ), and yellow pod color (Y) is
dominant to green pod color (y) in pea plants. A pure-breeding green plant with full pods is
crossed with a pure-breeding yellow plant with constricted pods. The offspring are then
testcrossed. What is the expected phenotypic ratio of the offspring?
a. 1:2:1; b. 3:1; c. 1:1:1:1; d. 9:3:3:1; e. 9:7
8. Full pod shape (F) is dominant to constricted pod shape (f ), and yellow pod color (Y) is
dominant to green pod color (y) in pea plants. What is the genotype of a yellow plant with a
constricted pod?
a. FFYY; b. ffYY; c. Ffyy; d. ffyy; e. two of these choices 2
9. How many different phenotypes can be expressed in a character controlled solely by a one
gene, two-allele system, in which the alleles are codominant?
a. one; b. two; c. three; d. five; e. ten
10. A woman of blood type O has a type O child. A man of which blood type could have been
the father?
a. A; b. B; c. AB; d. O; e. more than one of these
11. Which of the following could be the blood type of a father of a type A child with an AB
mother?
a. A; b. B; c. O; d. two of these choices; e. all of these choices
12. How many tetrads are there in metaphase I of meiosis in human beings?
a. 2; b. 22; c. 23; d. 46; e. 92
13. Segregation and independent assortment (as defined by Mendel) occur during
a. metaphase of mitosis; b. metaphase of meiosis I; c. anaphase of meiosis I;
d. anaphase of meiosis II; d. metaphase of meiosis II.
14. Identify the stage of cell division and the diploid number of the cell in figure below.
a. metaphase of mitosis, 2n = 4; b. metaphase I of meiosis, 2n = 4
c. metaphase I of meiosis, 2n=8; d. metaphase II of meiosis, 2n=4
e. none of these choices
15. Identify the stage of cell division and the diploid number of the cell in figure below.
3
a. metaphase of mitosis, 2n = 4
b. metaphase I of meiosis, 2n = 2
c. metaphase I of meiosis, 2n = 4
d. metaphase II of meiosis, 2n = 4
e. none of these choices
16. What process and what ploidy number of the parent organism are shown in the cell in below?
a. mitosis, 2n = 4; b. mitosis, 2n = 8; c. meiosis I, 2n = 2; d. meiosis I, 2n = 4;
e. meiosis II, 2n = 4
17. How many chromosomes (as opposed to chromatids) are there in metaphase II of meiosis in
human beings?
a. two; b. twenty-two; c. twenty-three; d. forty-six; e. ninety-two
18. The stage between mitoses in eukaryotic cells is called
a. prophase; b. interphase; c. telophase; d. cytophase; e. none of these choices
19. A dihybrid plant was crossed; the F2 generation consisted of: 860 tall plants with purple
flowers; 285 dwarf, purple plants; 340 tall, pink plants; and 115 dwarf, pink plants. The data
remind you of a 9:3:3:1 ratio. What is the chi-square value in the test of this hypothesis?
a. 0.377; b. 7.5; c. 10.11; d. 11.08; e. 15.78
20. A dihybrid plant was crossed; the F2 generation consisted of: 860 tall plants with purple
flowers; 285 dwarf, purple plants; 340 tall, pink plants; and 115 dwarf, pink plants. The data
remind you of a 9:3:3:1 ratio. How many degrees of freedom apply to the test of this hypothesis?
a. zero; b. one; c. three; d. four; e. 15
21. A dihybrid plant was crossed; the F2 generation consisted of: 860 tall plants with purple
flowers; 285 dwarf, purple plants; 340 tall, pink plants; and 115 dwarf, pink plants. The data
remind you of a 9:3:3:1 ratio. The critical chi-square for two degrees of freedom (d.f.) = 5.991;
three d.f. = 7.815; four d.f. = 9.488; nine d.f. = 16.919. Therefore, you should
a. reject your hypothesis; b. accept your hypothesis; 4
c. perform a backcross; d. fudge your data;
e. use a lower critical chi-square value
22. A dihybrid (AaBb) lab mouse is testcrossed. What is the probability that the first three
offspring are dihybrid females?
a. 3(1/8) = 0.375; b. (1/4)
3
= 0.016; c. (1/8)
3
= 0.002
d. 3(1/4) = 0.75; e. 3(1/2) = 1.50
23. What is the probability that a gamete formed in a female in a Drosophila species with 2n = 10
will have only paternal centromeres?
a. (1/2)
10
= 0.001; b. (1/2)
5
= 0.031; c. (1/2)
2
= 0.25; d. (1/2) = 0.5; e. (1/4)
5
= 0.001
24. A male fruit fly and a female fruit fly are heterozygous for detached wings (det). What is the
probability that of their first ten offspring, any five will be females with detached wings?
a. (1/4)
5
(3/4)
5
; b. (1/8)
5
(3/8)
5
; c. (10!/5!5!)(1/8)
5
(3/8)
5
d. (10!/5!5!)(1/8)
5
(7/8)
5
; e. none of these choices
25. A trihybrid plant, exhibiting independent assortment at all three loci, is self-fertilized. What
is the probability that an offspring will have the dominant phenotype at all three loci?
a. 1/2; b. 1/8; c. 9/16; d. 1/64; e. 27/64
26. An organism is diploid with an XYY sex chromosome complement. It would be a
a. male fly, male human being;
b. male fly, female human being
c. female fly, male human being;
d. female fly, female human being
e. intersex fly, male human being
27. An organism is diploid with an XXY sex chromosome complement. It would be a
a. male fly, male human being;
b. male fly, female human being
c. female fly, male human being;
d. female fly, female human being
e. intersex fly, male human being
28. How many Barr bodies are found in the nuclei of an XYY human male?
a. zero; b. one; c. two; d. three; e. unpredictable
29. How many Barr bodies would a cell from an XXYY human being have?
a. none; it's male; b. none; it's female; c. one; d. two; e. three
30. If a fruit fly is a normal diploid for its autosomes but has one X and no Y chromosomes, what
sex is it?
a. male; b. female; c. intersex; d. metafemale; e. none of these choices 5
31. A woman whose husband worked at the Chernobyl nuclear reactor gives birth to a
hemophilic son.
a. She should blame the reactor accident because the radiation might have caused the
hemophilia.
b. She should not blame the accident because she carried the hemophilia allele.
c. Her husband should sue for divorce because it can't be his child.
d. Further genetic tests should be done to determine who is at fault.
e. Hemophilia is environmentally induced, not genetic.
32. If the father and all his daughters but none of his sons have a genetic disease, how is the trait
most likely inherited?
a. autosomal dominant; b. autosomal recessive; c. X-linked dominant;
d. X-linked recessive; e. holandric
33. Barring new mutation, and assuming complete penetrance and single-locus inheritance,
what are possible modes of inheritance of the trait shown in figure below?
a. autosomal recessive; b. autosomal dominant;
c. X-linked recessive; d. X-linked dominant;
e. more than one of these.
34. Barring new mutation, and assuming complete penetrance and single-locus inheritance,
what are possible modes of inheritance of the trait shown in figure below?
a. autosomal recessive; b. autosomal dominant;
c. X-linked recessive; d. X-linked dominant;
e. more than one of these. 6
35. A plant of genotype CCdd is crossed to ccDD and an F1 testcrossed to ccdd. If the genes are
linked, and 20 cM apart, the percentage of ccdd recombinants will be
a. 10. b. 20. c. 25. d. 50. e. 75.
36. In Drosophila, the two genes w and sn are X-linked and 25 map units apart. A female fly of
genotype w
+
sn
+
/w sn is crossed to a male from a wild-type line. What percent of male progeny
will be w
+
sn?
a. 0; b. 12.5; c. 25; d. 37.5; e. 50.
37. In maize, two plants that are heterozygous for the recessive alleles a and b are crossed, what
frequency of double-mutant progeny will appear if a and b are 7.2 map units apart, and both
parents carry a and b in trans (configuration)?
a. 0.036; b. 0.0625; c. 0.001296 d. 0.005184; e. 0.072.
38. In a four-point testcross the number of phenotypic classes of progeny expected is
a. 16; b. 8; c. 81; d. 4; e. cannot be determined.
39. The following recessive alleles are found in corn: g, glossy leaf and r, red aleurone. A hybrid
of unknown origin is testcrossed, with the following 1,000 progeny resulting: red, 127; glossy,
153; wild-type, 352; and glossy + red, 368. Which of the following could have been a parent of
the dihybrid, assuming the parents were homozygous?
a. glossy, red; b. glossy; c. red; d. more than one of these; e. none of these choices
40. The following recessive alleles are found in corn: g, glossy leaf and r, red aleurone. A hybrid
of unknown origin is testcrossed, with the following 1,000 progeny resulting: red, 127; glossy,
153; wild-type, 352; and glossy + red, 368. What is your best estimate of the map distance
between glossy and red, in map units?
a. 12.7; b. 15.3; c. 28.0; d. 36.8; e. 56.0
41. Genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map
units apart. If a triple heterozygote is testcrossed, among 1,000 progeny, how many are expected
to result from double crossovers if there is no interference?
a. 10; b. 20; c. 30; d. 60; e. can't be determined
42. Genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map
units apart. If a triple heterozygote is testcrossed, among 1,000 progeny, how many are expected
to result from double crossovers if interference = 0.5?
a. 10; b. 20; c. 30; d. 60; e. can't be determined
43. Genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map
units apart. If a triple heterozygote is testcrossed, among 1,000 progeny, how many are expected
to result from single crossovers between a and b if there is no interference?
a. 20; b. 40; c. 60; d. 80; e. none of the above 7
44. Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a),
hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that
was testcrossed, the phenotypes in figure 5 below were observed. What is the linkage
arrangement of these three loci?
259 hairless 268 anthocyaninless, jointless, hairless
40 jointless, hairless 941 anthocyaninless, hairless
931 jointless 32 anthocyaninless
260 normal 269 anthocyaninless, jointless
a. h-a-j. b. a-h-j. c. a-j-h. d. j-h-a. e. two of these choices.
45. Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a),
hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that
was testcrossed, the phenotypes in figure 5 above were observed. If the parentals (P1) were
homozygous, which of the following could have been a parental?
a. anthocyaninless. b. jointless. c. anthocyaninless, jointless.
d. hairless, jointless. e. hairless.
46. Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a),
hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that
was testcrossed, the phenotypes in figure 5 above were observed. What is your best estimate of
the anthocyaninless-hairless distance?
a. 20.0. b. 35.2. c. 37.6. d. 40.0. e. 60.0.
47. Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a),
hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that
was testcrossed, the phenotypes in figure 5 above were observed. What is your best estimate of
the anthocyaninless-jointless distance?
a. 20.0. b. 35.2. c. 37.6. d. 40.0. e. 60.0.
48. Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a),
hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that
was testcrossed, the phenotypes in figure 5 were observed. What is your best estimate of the
hairless-jointless distance?
a. 20.0. b. 35.2. c. 37.6. d. 40.0. e. 60.0.
49. Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a),
hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that
was testcrossed, the phenotypes in figure 5 were observed. Approximately what is the coefficient
of coincidence?
a. 0.4 b. 0.5 c. 0.6 d. 1.8 e. irrelevant 8
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