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GENETICS HW
AP BIO
DR WEINER
Multiple Choice (1 pt)
1. In Drosophila the traits for red eye color (R) and straight wings (W) are dominant and the traits for sepia
eyes (r) and curly wings (w) are recessive. A cross between two flies produces a progeny with 607 red
eyed flies with straight wings, and 202 red eyed flies with curly wings. Assuming neither of these genes
is sex linked, which of the following are MOST LIKELY to be the genotypes of the parents?
a. RRWW x RRWW
b. RRWW x RRWw
c. RrWw x RrWw
d. RRWw x RRWw
2. Red-green colorblindness is a sex-linked recessive trait in humans. Which of the following is true if a
colorblind woman and a man with normal vision have children?
a. None of their children will be colorblind
b. Half of their male children will be colorblind
c. Half of their female children will be colorblind
d. All of their male children will be colorblind
3. If alleles R and S are on two different chromosomes, and the probability of allele R segregating into a
gamete is ¼ and the probability of allele S segregating into a gamete is ½, what is the probability they
will both segregate into the same gamete?
a. ½ x ¼
b. ½+ ¼
c. ½ x ½
d. ¼ x ¼
The following questions refer to an individual with type O blood, whose mother has type A blood
4. The father must have which of the following blood types?
a. A, B, or O
b. AB or A
c. AB or B
d. O only
5. If the type O individual were to mate with a person with type AB blood, which of the following is the
bet calculation of the ratio of their offspring?
a. 3 IAi: 1 IBi
b. 1 IAi:2IAIB:1IBi
c. IAi:IBi
d. 3IAi:1ii
6. Two yellow mice with the genotype Yy are mated. After many offspring, 2/3 are yellow and 1/3 are not
yellow (a 2:1 ratio). Mendelian genetics dictates that this cross should produce offspring that were ¼
YY(yellow), ½ Yy(yellow), ¼ yy(not yellow). What s the most likely conclusion from this experiment?
a. The mice did not bear enough offspring for the ratio calculation to be specific
b. The Y allele is lethal in the homozygous form causing death early in embryonic development
c. A mutation occurred masking the effect of the Y allele
d. Nondisjunction occurred
7. Cystic fibrosis affects the lungs, the pancreas, the digestive and other organs, resulting in symptoms
ranging from breathing difficulties yo recurrent infections. Which of the following terms best describes
this?
a. Incomplete dominance
b. Pleiotropy
c. X-inactivation
d. Epistasis
Questions 8-11 refer to the following:
A woman whose blood type is A+ has a daughter who is O+ and a son who is B-. Rh positive is a trait that
shows simple dominance over Rh negative where R = positive and r = negative. A third gene for the MN blood
group has codominant alleles M and N.
8. Which of the following is a possible partial genotype for the son?
a. IBIB
b. IBIA
c. ii
d. IBi
9. Which of the following is a possible genotype of the mother?
a. IAIA
b. IAIB
c. ii
d. IAi
10. Which of the following is a possible phenotype for the father?
a. Ab. Oc. B+
d. AB11. If both children are of blood M, which of the following is possible?
a. Each parent is either M or MN
b. Each parent must be M
c. Neither parent can have the N allele
d. Both children are heterozygous for this gene
12. In cats, black fur is caused by an X-linked allele; the other allele at this locus causes orange color. The
heterozygote is tortoiseshell. What kinds of offspring would you expect from a cross between a black
female cat and an orange male cat?
a. Tortoiseshell females; tortoiseshell males
b. Black females; tortoiseshell males
c. Tortoiseshell females; black males
d. Orange females; black males
13. Red-green colorblindness is a sex-linked recessive trait in humans. Two people with normal color vision
have a colorblind son. What are the genotypes of the parents?
a. XbXb x XBY
b. XBXB x XbY
c. XBXb x XBY
d. XBXb x XbY
Questions 14-16 refer to the following pedigree
I-I
I-II
II-I
III-I
II-II
III-II
= affected female
= affected male
14. Which of the following is true about the trait in the illustrated pedigree?
a. It Is a sex-linked trait
b. It is a dominant trait
c. Individual III-I is free of the trait
d. Individual I-II is a carrier
15. The probability of individual II-II being a carrier for the condition is
a. 0%
b. 25%
c. 50%
d. 100%
16. If the trait confers survival , which of the following is true about future generations?
a. The number of recessive individuals will decrease
b. The number of heterozygote individuals will decrease
c. The dominant allele will increase in the population
d. The recessive phenotype will increase
17. The pedigree below illustrates the inheritance pattern for hemophilia in a family. What is the probability
that female #5 is likely to have a son who is a hemophiliac if she marries a man with hemophilia?
1
3
a.
b.
c.
d.
2
4
5
100%
50%
25%
0%
18. A woman with an inherited skin condition and her husband, with no family history of the condition,
have a female child that develops the trait. The mother’s father also had the trait but her mother did not.
The trait is known to be inherited as a dominant gene. Which of the following can be stated with
confidence about the inheritance of this gene?
a. The trait is autosomal dominant
b. The trait is sex-linked
c. The mother is homozygous dominant
d. The daughter had a 50% probability of inheriting the trait
Questions 19-22: The following Punnett square illustrates the phenotypes of the offspring that may result from
the mating of two black mice, heterozygous for 2 genes located on separate chromosomes
BbCc X BbCc
BC
bC
Bc
bc
BC
BBCC
(black) #1
BbCC
(black) #5
BBCc
(black) #9
BbCc
(black) #13
bC
BbCC
(black) #2
bbCC
(gray) #6
BbCc
(black) #10
bbCc
(gray) #14
Bc
BBCc
(black) #3
BbCc
(black) #7
BBcc
(white) #11
Bbcc
(white) #15
bc
BbCc
(black) #4
bbCc
(gray) #8
Bbcc
(white) #12
bbcc
(white) #16
19. Which of the following is a true statement about the relationship between these two gene pairs?
a. Gene C is dominant over either gene b or B.
b. Genotype cc prevents the expression of either genotype BB or Bb.
c. Genotypes BB and Bb prevent the expression of genotype cc.
d. Genotypes CC and Cc prevent the expression of genotypes BB and Bb.
20. Which of the following types of inheritance best describes the pattern illustrated in the Punnet square?
a. epistasis
b. co-dominance
c. sex linked
d. pleiotropy
21. Which of the following best describes the variation in the offsprings’ genotypes?
a. crossing over
b. random mutation
c. independent assortment
d. gene linkage
22. Which of the following would be the expected phenotypic ratio of the offspring produced by #13 and
#16?
a. 50% black and 50% white
b. 25%black, 50% gray, 25%white
c. 25%black, 25%gray, 50%white
d. 50%black, 25%gray, 25%white
23. Females who are heterozygous for hemophilia typically have somewhat slower clotting times than
homozygous dominant females who would not be carrying this gene. Which of the following is the best
explanation for this phenomenon?
a. Females carry another gene pair that is turned on by the presence of the hemophilia gene
b. The male hemophilia gene is dominant in females and recessive in males
c. The gene mutates readily and becomes dominant
d. Because of Barr bodies, some cells have a single active gene for the normal trait, some have a
single active gene for the hemophilia trait.
Questions 24-27:
P1
Wild type drosophila
(grey with normal wings)
F1
Wild type
x
ebony
Vestigial
wild type drosophila
(grey with normal wings)
grey
vestigial
ebony
normal
You and your lab partner are given a culture of phenotypically wild, identical drosophila. You are informed that
these are heterozygotes and you have been asked to determine what the “hidden” traits are and to determine
how they are inherited using only the drosophila in the culture. When you cross the drosophila, you obtain the
following number of offspring. There are approximately equal numbers of male and female for each phenotype.
Wild type
129
Ebony vestigial
15
Grey vestigial
33
Ebony normal
32
Total flies
209
24. Based on the counts supplied in this problem, which of the following would you hypothesize from your
data before doing the chi square test?
a. the genes for grey and vestigial are both dominant
b. the genes for wing length and body color are both located on the same chromosome
c. the genes for body color and wing length are inherited independently
d. the gene for wing length is sex linked
25. What F1 phenotype ratio would you expect if the genes for body color and wing length are autosomal
and independently assort?
a. 1:1:1:1
b. 1:2:2:1
c. 9:3:3:1
d. 4:3:2:1
26. In order to use a chi square test of significance, you must assume a null hypothesis. Which of the
following is the best statement about the null hypothesis?
a. There is no relationship between the observed and expected results
b. The data will fall within acceptable limits
c. There is a small but insignificant difference between the observed and expected results
d. There is a difference between the observed and expected results
The data from the chi square test is as follows:
expected
observed
Wild
118
129
Ebony normal
39
32
Grey vestigial
39
33
Ebony vestigial
13
15
total
209
209
Critical values table:
Degrees of .99
freedom
1
.000157
O-E
11
-7
-6
2
(O-E)2
121
49
36
15
Σ(O-E)2/E
1.025
1.256
0.923
0.308
3.512
.95
.80
.50
.20
0.05
.01
0.00393
0.0642
0.455
1.642
3.841
6.635
2
3
4
0.020
0.115
0.297
0.103
0.352
0.711
0.446
1.005
1.649
1.386
2.366
3.357
3.219
4.642
5.989
5.991
7.815
9.488
9.210
11.345
13.277
27. If the minimum probability for rejecting the null hypothesis is a confidence level of 0.05, what can you
conclude about your data?
a. The null hypothesis must be rejected, the genes for body color and wing length are linked
b. The null hypothesis must be rejected, the genes for body color and wing length are independently
inherited
c. The null hypothesis must be accepted, the genes for body color and wing length are linked
d. The null hypothesis must be accepted, the genes for body color and wing length are independently
inherited
28. Given the parents AABBCc x AabbCc, assume simple dominance for each trait and independent
assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?
a. ¼
b. 1/8
c. ¾
d. 1
Problems (6 pts)
1. Given two separate, independently assorting genes, A and B, with A dominant to a and B dominant to b,
answer the following questions:
a. What is the probability of getting an AB gamete from an individual who is heterozygous at both loci?
Show how you came up with this.
b. What is the probability of getting an AABB child from two parents that are heterozygous at both loci?
Show your work.
c. From a cross between two individuals that are heterozygous at both loci, what is the probability that an
offspring will express the dominant phenotype at both loci?
2. Two organisms with the genotypes AabbCc and AaBbcc are mated. What is the probability of having an
offspring with AT LEAST TWO homozygous recessive traits?
3. Eleanor Perkiness is phenotypically normal, but her family has its share of sex-linked abnormalities. Her
husband, Garvey, has the X-linked dominant allele for brown-spotted teeth but is otherwise normal. Her
brother Arthur and her son Little Chester, both suffer from hemophilia A, the most common type of sexlinked bleeder’s disease. Her father, Grandpa, is not hemophilic, but is colorblind. One morning, Grandpa
came downstairs wearing one red sock and one green sock. When Little Chester did not notice it, Eleanor
realized that Chester was also colorblind.
a. Write the genotypes for: Eleanor, Garvey, Little Chester, and Grandpa:
XH = normal, Xh = hemophilia, XB = normal, Xb = colorblind X,T = brown tooth, Xt = normal
b. Eleanor and Garvey are expecting another child. If it is a daughter, what is the probability that it will be:
Hemophilic
Colorblind
Brown-toothed
c. If their child is a son, what is the probability that he will be:
Hemophilic
Colorblind
Brown-toothed
4. A woman is married for the second time. Her first husband had blood type A and her child by that marriage
had blood type O. Her new husband has blood type B and their child is blood type AB. What is the woman’s
genotype for blood type?
5. Four babies are born in the hospital and each has a different blood type : A, B, AB, and O. The parents of
these babies have the following pairs of blood types : A and B, O and O, AB and O, B and B. Which baby
belongs to which set of parents?
6.
In corn plants P = purple kernel color and p = red kernel color. At a separate locus (gene location) the I
gene is epistatic: I= inhibits kernel color and i= permits kernel color. If two plants that are heterozygous at
both loci are crossed, what are the phenotypes of the offspring plants? Include what genotypes will yield
each phenotype.
7. Determine the mode of inheritance of this trait in the following pedigree. Explain your answer and
determine the genotypes of all members of the family.
8. In a cross between 2 individuals that are AaBbCcDd and assuming independent assortment of all 4 genes,
what are the probabilities that the offspring will be:
a. aabbccdd
b. AaBbCcDd
c. AaBBccDd
9. Imagine that a newly discovered, recessively inherited disease (D = normal d = disease) is expressed only in
individuals with type O blood, although the disease and blood group are independently inherited. A normal
man with type A blood and a normal woman with type B blood already have one child with the disease. The
woman is now pregnant for the second time. What is the probability that the second child will also have this
disease? Assume both parents are heterozygous for the disease gene.
10. A man has six fingers on each hand and six toes on each foot. Extra digits is a dominant trait. His wife and
their daughter have the normal number of digits. What fraction of the parents’ children would be expected to
have extra digits?
11. In mice, black color (B) is dominant to white (b). At a different locus, a dominant allele (A) produces a
band of yellow at the tip of each hair in mice with black fur. This gives a frosted appearance known as
agouti. Expression of the recessive allele results in solid coat color. If 2 mice that are heterozygous at both
loci are mated, what will be the genotypes of the offspring and the expected phenotypic ratios?
12. Refer to the following pedigree:
What inheritance pattern can BEST explain the disorder in this pedigree? Explain your answer. Based upon
your decision of the pattern of inheritance for this disorder, what is the genotype at the top of the tree? Explain
your answer