Genetics 311, Practice Problem Set 2

1.  Show the types and expected frequencies of gametes produced by individuals of the following genotypes: AABbCc, AaBBCcDd, AABbCcdd.

2. What are the probabilities of obtaining:
a)   An AbC gamete from an AaBbCc individual.
b)   An AaBBCC zygote from the cross AaBbCc x AaBbCC.
c)   An abC phenotype from the cross AaBbCc x aaBbCC.
d)   An AB gamete from an AaBb individual.
e)   An AB gamete from an AABb individual.
f)   An AABB zygote from the cross AaBb x AaBb.
g)  An AABB zygote from the cross aabb x AABB
h)  An AB phenotype from the cross AaBb x AaBb.
i)  An AB phenotype from the cross aabb x AABB.
j)  An aB phenotype from the cross AaBb x AaBB.

3.  Heterozygous black guinea pigs (Bb) are intercrossed.  What is the probability of obtaining:
a)  four whites.
b)  black-white-white-black.
c)  black-white-black or white-black-white.
d)  two black females.
e)  a black female or a white male.
f)  female or white.
g)  four whites and then three blacks.
h)  four whites and three blacks, any order.
i)   three whites and four blacks, any order.
j)   five males and two females, any order.
k)  ten whites, or nine whites and one black in any order.

4.  What is the mode of inheritance for the rare genetic trait pedigreed below?

What is the probability that the following individuals carry the trait:
(A) I 3,   (B) II 4,   (C) II 11,   (D) III 1,   (E) III 3,   (F) III 5

 5.  In 1901, Bateson reported the first post-Mendelian study of a cross involving two characters.  White leghorn chickens, having white feathers and large "single" combs, were crossed to Indian Game Fowl, having dark feathers and small "pea" combs.  The F1 were white with pea combs, and the F2 distribution was: 111 white pea, 37 white single, 34 dark pea, and 8 dark single.  What phenotypic ratio would you expect?  Test your prediction using chi-square.

6.  In rumbunnies large ears (E) is dominant to small ears (e) and tufted ears (T) is dominant to shaven ears (t).  Two heterozygous rumbunnies are crossed, with the following results: 420 large tufteds, 189 small shavens, and 141 large shavens.  How well do these results correspond with expectation if large ears are epistatic over ear hair length?  If small ears are epistatic over ear hair length?  Use chi-square.

7.  Double heterozygotes were crossed to recessive parents and the following progeny ratios observed.  For each case decide whether the loci are linked or independently-assorting.  If the loci are linked, what is the map distance?

               AB      Ab      aB       ab
        a)    15     140     160       25
        b)  180     165     185     180
        c)  180       40       40     180
        d)    27       24       32       31
        e)    45       14       16       45

8.  A male Drosophila with cut wings, vermilion eyes, and yellow body was crossed to a triply-heterozygous female, with the following result:

    yellow                    440                       vermilion                         300
    yellow, vermilion      50                       yellow, vermilion, cut     1710
    wild type              1780                       yellow, cut                      270
    vermilion, cut          470                       cut                                   55

Give the gene sequence, map distances, and coefficient of coincidence.

2.  (a) 1/8,   (b) 1/16,   (c) 1/8,   (d) 1/4,   (e) 1/2,   (f) 1/16,   (g) 0,   (h) 9/16,   i) 1.0,   j) 1/4.
3.  (a) 0.0039,   (b) 0.035,   (c) 0.187,   (d) 0.141,   (e) 0.5,   (f) 0.625,   (g) 0.0016,
        (h) 0.058,   (i) 0.173,   (j) 0.164,   (k) 2.96 x 10-5
4.  Autosomal recessive.  (a) 1.0,   (b) 1.0,   (c) 2/3,   (d) 1/2,   (e) 2/3,   (f) 1/3.
5.  Expect 9:3:3:1.  Chi square = 1.62, ns with 3 df
6.  F2 phenotypes wrong for large ears epistatic over ear hair.  If small ears epistatic
    over ear hair, expect 9:3:4, chi-square = 0.036, ns with 2 df.
7.  (a) 12 mu,   (b) not linked,   (c) 18 mu,   (d) not linked,   (e) 25 mu.
8.  y---20---ct---13---v    CofC = 0.80

Genetics home   Return to Genetics 311 page