Exam
Name___________________________________

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Name at least three scientists who, around the year 1900, were influential in setting the stage for our present understanding of transmission genetics.
A) de Vries, Correns, Tschermak, Sutton, Boveri
B) Hippocrates, Aristotle, Kolreuter
C) Darwin, Mendel, Lamarck
D) Watson, Crick, Wilkins, Franklin
E) Beadle, Tatum, Lederberg

1)

2) Name the individual whose work in the mid-1800s contributed to our understanding of the particulate nature of inheritance as well as the basic genetic transmission patterns. With what organism did this person work?
A) George Beadle, Neurospora
B) Thomas Hunt Morgan, Drosophila (fruit fly)
C) Boris Ephrussi, Ephestia
D) Calvin Bridges, Drosophila (fruit fly)
E) Gregor Mendel, Pisum sativum

2)

3) A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their remaining offspring would be expected to have normal pigmentation?
A) 25%
B) 50%
C) about 66%
D) about 90%
E) 75%

3)

4) Polydactyly is expressed when an individual has extra fingers and/or toes. Having extra digits is caused by a dominant allele. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly?
A) 7/16
B) 1/2
C) 3/4
D) 1/8
E) 1/32

4)

5) Tightly curled or wooly hair is caused by a dominant gene in humans. If a heterozygous curly-haired person marries a person with straight hair, what fraction of their offspring would be expected to have straight hair?
A) 1/2 straight
B) 1/4 straight
C) 3/4 straight
D) 100% straight
E) It is impossible to predict the outcome.

5)

6) What types of phenotypic ratios are likely to occur in crosses when dealing with a single gene pair where all the genotypic combinations are of equal viability?
A) 2:3, 1:2
B) 9:3:3:1, 27:9:9:9:3:3:3:1
C) 1:2:1, 3:1
D) 1:4:6:4:1, 1:1:1:1
E) 12:3:1, 9:7

6)

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7) Assume that a black guinea pig crossed with an albino guinea pig produced five black offspring.
When the albino was crossed with a second black one, four black and three albino offspring were produced. What genetic explanation would apply to these data?
A) albino = recessive; black = dominant
B) albino and black = codominant
C) albino = dominant; black = incompletely dominant
D) albino = recessive; black = recessive
E) none of the above

7)

8) The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus is called
A) continuous variation.
B) independent assortment.
C) dominance or recessiveness.
D) discontinuous variation.
E) segregation.

8)

9) The chi-square test involves a statistical comparison between measured (observed) and predicted
(expected) values. One generally determines degrees of freedom as
A) the sum of the two categories.
B) one less than the number of classes being compared.
C) ten minus the sum of the two categories.
D) the number of categories being compared.
E) one more than the number of classes being compared.

9)

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
10) Assume that in a series of experiments, plants with round seeds were crossed with plants with wrinkled seeds and the following offspring were obtained: 220 round and 180 wrinkled. 10)

(a) What is the most probable genotype of each parent?
(b) What genotypic and phenotypic ratios are expected?
(c) Based on your answer to part (b), what are the expected (theoretical) numbers of progeny (400 total) of each phenotypic class?

11) In peas, gray seed color is dominant to white. For the purposes of this question, assume that Mendel crossed plants with gray seeds with each other and the following progeny were produced: 320 gray and 80 white.
(a) What is the most probable genotype of each parent?
(b) What genotypic and phenotypic ratios are expected in the progeny of such a cross?

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11)

12) Assume that you have a garden and some pea plants have solid leaves and others have striped leaves. You conduct a series of crosses (a through e) and obtain the results given in the table.

Cross
(a)
(b)
(c)
(d)
(e)

Solid

solid X striped solid X solid striped X striped solid X solid solid X striped

Progeny

55
36
0
92
44

12)

Striped
60
0
65
30
0

Define gene symbols and give the possible genotypes of the parents of each cross.

13) The phenotype of vestigial (short) wings (vg) in Drosophila melanogaster is caused by a recessive mutant gene that independently assorts with a recessive gene for hairy (h) body.
Assume that a cross is made between a fly with normal wings and a hairy body and a fly with vestigial wings and normal body hair. The wild-type F1 flies were crossed among each other to produce 1024 offspring. What phenotypes would you expect among the 1024 offspring, and how many of each phenotype would you expect?

13)

14) Two organisms, AABBCCDDEE and aabbccddee, are mated to produce an F1 that is self-fertilized. If the capital letters represent dominant, independently assorting alleles,

14)

(a) how many different genotypes will occur in the F2?
(b) what proportion of the F2 genotypes will be recessive for all five loci?
(c) would you change your answers to parts (a) and/or (b) if the initial cross occurred between AAbbCCddee X aaBBccDDEE parents?
(d) would you change your answers to parts (a) and/or (b) if the initial cross occurred between AABBCCDDEE X aabbccddEE parents?

15) How many different kinds of gametes can be produced by an individual with the genotype
AABbCCddEeFf?

15)

16) Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a).
Two parents with normal pigmentation have an albino child.

16)

(a) What is the probability that their next child will be albino?
(b) What is the probability that their next child will be an albino girl?
(c) What is the probability that their next three children will be albino?

17) Dentinogenesis imperfecta is a rare, autosomal, dominantly inherited disease of the teeth that occurs in about one in 8000 people The teeth are somewhat brown in color, and the crowns wear down rapidly. Assume that a male with dentinogenesis imperfecta and no family history of the disease marries a woman with normal teeth. What is the probability that
(a) their first child will have dentinogenesis imperfecta?
(b) their first two children will have dentinogenesis imperfecta?
(c) their first child will be a girl with dentinogenesis imperfecta?

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17)

18) A certain type of congenital deafness in humans is caused by a rare autosomal (not
X-linked) dominant gene.

18)

(a) In a mating involving a deaf man and a deaf woman (both heterozygous), would you expect all the children to be deaf? Explain your answer.
(b) In a mating involving a deaf man and a deaf woman (both heterozygous), could all the children have normal hearing? Explain your answer.
(c) Another form of deafness is caused by a rare autosomal recessive gene. In a mating involving a deaf man and a deaf woman, could some of the children have normal hearing?
Explain your answer.

19) Among dogs, short hair is dominant to long hair and dark coat color is dominant to white
(albino) coat color. Assume that these two coat traits are caused by independently segregating gene pairs. For each of the crosses given below, write the most probable genotype (or genotypes if more than one answer is possible) for the parents. It is important that you select a realistic symbol set and define each symbol below.

19)

Phenotypes of Offspring

Parental Phenotypes
(a)
(b)
(c)
(d)

dark, short X dark, long albino, short X albino, short dark, short X albino, short dark, short X dark, short

Short
Dark

Long
Dark

26
0
16
175

Short
Albino

24
0
0
67

0
102
16
61

Long
Albino
0
33
0
21

Assume that for cross (d) above you were interested in determining whether fur color follows a 3:1 ratio. Set up (but do not complete the calculations) a chi-square test for these data [fur color in cross (d)].

20) What phenotypic ratio is likely to occur in crosses when dealing with two completely dominant, independently segregating gene pairs, when both parents are fully heterozygous? 20)

21) Provide simple definitions that distinguish segregation and independent assortment.

21)

22) In what ways is sample size related to statistical testing?

22)

23) In a chi-square analysis, what condition causes one to reject (fail to accept) the null hypothesis? 23)

24) If one is testing a goodness of fit to a 9:3:3:1 ratio, how many degrees of freedom would be associated with the chi-square analysis?

24)

25) Assuming no crossing over between the gene in question and the centromere, when do alleles segregate during meiosis?

25)

26) Assuming a typical monohybrid cross in which one allele is completely dominant to the other, what ratio is expected if the F1s are crossed?

26)

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27) Under what conditions does one expect a 9:3:3:1 ratio?

27)

28) Under what conditions does one expect a 1:1:1:1 ratio?

28)

29) What is the probability of flipping a penny and a nickel and obtaining one head and one tail? 29)

30) How many different kinds of gametes will be expected by an individual with the genotype
PpCcTTRr?

30)

31) Assume that a chi-square test was conducted to test the goodness of fit to a 9:3:3:1 ratio and a chi-square value of 10.62 was obtained. Should the null hypothesis be accepted?

31)

32) Assume that a chi-square test was conducted to test the goodness of fit to a 3:1 ratio and a chi-square value of 2.62 was obtained. Should the null hypothesis be accepted? How many degrees of freedom would be associated with this test of significance?

32)

33) Assume that a chi-square test provided a probability value of 0.02. Should the null hypothesis be accepted?

33)

34) In studies of human genetics, usually a single individual brings the condition to the attention of a scientist or physician. When pedigrees are developed to illustrate transmission of the trait, what term does one use to refer to this individual?

34)

35) Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a).
Two parents with normal pigmentation have an albino child. What is the probability that their next child will be albino?

35)

36) Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a).
Two parents with normal pigmentation have an albino child. What is the probability that their next child will be an albino girl?

36)

37) Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a).
Two parents with normal pigmentation have an albino child. What is the probability that their next three children will be albino?

37)

38) The autosomal (not X-linked) gene for brachydactyly, short fingers, is dominant to normal finger length. Assume that a female with brachydactyly in the heterozygous condition is married to a man with normal fingers. What is the probability that

38)

(a) their first child will have brachydactyly?
(b) their first two children will have brachydactyly?
(c) their first child will be a brachydactylous girl?

39) Tightly curled hair is caused by a dominant autosomal gene in humans. If a heterozygous curly-haired person marries a person with straight hair, what is the probability that their first three children will have straight hair?

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39)

40) A certain type of congenital deafness in humans is caused by a rare autosomal dominant gene. In a mating involving a deaf man and a deaf woman (both heterozygous), would you expect all the children to be deaf? Explain your answer.

40)

41) A certain type of congenital deafness in humans is caused by a rare autosomal dominant gene. In a mating involving a deaf man and a deaf woman, could all the children have normal hearing? Explain your answer.

41)

42) A certain type of congenital deafness in humans is caused by a rare autosomal recessive gene. In a mating involving a deaf man and a deaf woman, could some of the children have normal hearing? Explain your answer.

42)

43) For the purposes of this question, assume that being Rh+ is a consequence of D and that
Rh- individuals are dd. The ability to taste phenylthiocarbamide (PTC) is determined by

43)

the gene symbolized T (tt indicates nontasters). A female whose mother was Rh- has the
MN blood group, is Rh+ and a nontaster of PTC, and is married to a man who is MM, Rh-, and a nontaster. List the possible genotypes of the children. Assume that all the loci discussed in this problem are autosomal and independently assorting.

44) What conditions are likely to apply if the progeny from the cross AaBb X AaBb appear in the 9:3:3:1 ratio?

44)

45) Assume that a cross is made between a heterozygous tall pea plant and a homozygous short pea plant. Fifty offspring are produced in the following frequency:

45)

30 = tall
20 = short
(a) What frequency of tall and short plants is expected?
(b) If one wanted to test the goodness of fit between the observed and expected values, provide a statement of the null hypothesis.
(c) Compute a chi-square value associated with the appropriate test of significance.
(d) How many degrees of freedom are associated with this test of significance?

46) According to Mendel's postulate of ________, all possible combinations of gametes will be formed in equal frequency.

46)

47) Assuming independent assortment, what proportion of the offspring of the cross
AaBbCcDd X AabbCCdd will have the aabbccdd genotype?

47)

48) In a statistical sense, as the sample size increases, the average deviation from the expected fraction or ratio is expected to ________.

48)

49) In a chi-square test, as the value of 2 increases, the likelihood of rejecting the null hypothesis ________.

49)

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TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false.
50) Mendel's law of independent assortment is supported by a 1:1:1:1 testcross ratio.

50)

51) Mendel's law of segregation is supported by a 1:1 testcross ratio.

51)

52) Mendel's discoveries were well received and understood by his contemporaries.

52)

53) The nonfunctional form of a gene is called a wild-type allele.

53)

54) A gene can have a maximum of two alleles.

54)

55) To test Mendel's law of segregation, the experimenter needs a minimum of two contrasting forms of a gene.

55)

56) To test Mendel's law of independent assortment, the experimenter needs a minimum of two different genes and their two alleles.

56)

57) A 1:1 phenotypic ratio is expected from a monohybrid testcross with complete dominance.

57)

58) Assuming complete dominance, a 3:1 phenotypic ratio is expected from a monohybrid sib or self-cross. 58)

59) A 9:3:3:1 phenotypic ratio is expected from a dihybrid testcross.

59)

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Answer Key
Testname: UNTITLED3
1) A
2) E
3) E
4) B
5) A
6) C
7) A
8) E
9) B
10) (a) assuming that round (W) is dominant to wrinkled (w), Ww X ww
(b) 1:1 for both
(c) 200, 200
11) (a) using the symbols G = gray and g = white, Gg X Gg
(b) genotypic = 1:2:1, phenotypic = 3:1
12) (a) from cross (d), assume that solid (S) is dominant to striped (s): Ss X ss
(b) SS X SS or SS X Ss
(c) ss X ss
(d) Ss X Ss
(e) SS X ss
13) Phenotypes: wild, vestigial, hairy, vestigial hairy
Numbers expected: wild, 576; vestigial, 192; hairy, 192; vestigial hairy, 64
14) (a) 35 = 243
(b) 1/243
(c) no
(d) yes
15) 23 = 8

16) (a) 1/4
(b) 1/4 X 1/2 = 1/8
(c) 1/4 X 1/4 X 1/4 = 1/64
17) (a) 1/2
(b) 1/2 X 1/2 = 1/4
(c) 1/2 X 1/2 = 1/4
18) (a) No. In a mating involving heterozygotes, three genotypic classes are expected in the offspring: fully dominant, fully recessive, and heterozygous.
(b) It is possible that all of the children could have normal hearing.
(c) Since the gene in question is recessive, both of the parents are homozygous and one would not expect normal hearing in the offspring.
19) Let A = dark, a = albino and L = short, l = long
(a)
(b)
(c)
(d)

AALl X AAll or AALl X Aall aaLl X aaLl
AaLL X aaLL or AaLl X aaLL or AaLL X aaLl
AaL X AaLl

2=

(o — e)2
= (242 — 243)2/243 + (82 — 81)2 /81 e 20) 9:3:3:1
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Answer Key
Testname: UNTITLED3
21) Segregation is the separation of alleles during meiosis, while independent assortment states that a member of one gene pair has an equal and independent opportunity of segregating with either member of another gene pair.
22) By increasing sample size, one increases the reliability of the statistical test and decreases the likelihood of erroneous conclusions from chance fluctuations in the data.
23) usually when the probability value is less than 0.05
24) number of classes minus 1 = 3
25) meiosis I, when homologous chromosomes go to opposite poles
26) 3:1
27) dihybrid cross (F2 ) with independently assorting, completely dominant genes
28) This occurs in a cross involving doubly heterozygous individuals crossed to fully recessive individuals. The genes involved assort independently of each other.
29) 1/2 (apply the "sum law")
30) 8
31) no
32) yes; 1
33) no
34) proband
35) 1/4
36) 1/4 X 1/2 = 1/8
37) 1/4 X 1/4 X 1/4 = 1/64
38) (a) 1/2
(b) 1/2 X 1/2 = 1/4
(c) 1/2 X 1/2 = 1/4
39) 1/2 X 1/2 X 1/2 = 1/8
40) No. In a mating involving heterozygotes, three genotypic classes are expected in the offspring: fully dominant, fully recessive, and heterozygous.
41) Assuming that the parents are heterozygotes (because the gene is rare), it is possible that all of the children could have normal hearing.
42) Since the gene in question is recessive, both of the parents are homozygous and one would not expect normal hearing in the offspring.
43) MMDdtt, MMddtt, MNDdtt, MNddtt
44) complete dominance, independent assortment, no gene interaction
45) (a) 1:1 (25 tall and 25 short)
(b) The deviations from a 1:1 ratio (25 tall and 25 short) are due to chance.
(c) 2 = 2
(d) 1
46) independent assortment
47) zero
48) decrease
49) increases
50) TRUE
51) TRUE
52) FALSE
53) FALSE
54) FALSE
55) TRUE
56) TRUE
57) TRUE
58) TRUE

9

Answer Key
Testname: UNTITLED3
59) FALSE

10