1. The genotype of F1 individuals in a tetrahybrid cross is AaBbCcDd. Assuming independent
assortment of these four genes, what are the probabilities that F2 offspring will have the
following genotypes?
a. aabbccdd
¼ x ¼ x ¼ x ¼ = 1/256
b. AaBbCcDd
½ x ½ x ½ x ½ = 1/16
c. AABBCCDD
¼ x ¼ x ¼ x ¼ = 1/256
d. AaBBccDd
½ x ¼ x ¼ x ½ = 1/64
e. AaBBCCdd
½ x ¼ x ¼ x ¼ =1/128
2. What is the probability that each of the following pairs of parents will produce the indicated
offspring? (Assume independent assortment of all gene pairs.
a. AABBCC X aabbcc AaBbCc
1 x 1 x 1 =1
b. AABbCc X AaBbCc AaBbCC
½ *1/4 *1/4 = 1/32
c. AaBbCc X AaBbCc AABbCc
½ *1/2 *1/2 = 1/8
d. aaBbCC X AABbcc AaBbCc
1x½x1=½
3. In mice, black color (B) is dominant to white (b). At a different locus, a dominant allele (A)
produces a band of yellow just below the tip of each hair in mice with black fur. This gives a
frosted appearance known as agouti. Expression of the recessive allele (a) results in a solid coat
color. If mice that are heterozygous at both loci are crossed, what is the expected phenotypic
ratio of their offspring?
OMIT
4. In tigers, a recessive allele causes an absence of fur pigmentation (a "white tiger") and a crosseyed condition. If two phenotypically normal tigers that are heterozygous at this locus are
mated, what percentage of their offspring will be cross-eyed? What percentage will be white?
Aa x Aa  ¼ AA, ½ Aa, and ¼ aa, since the two are together it would be 25% for cross-eyed and
white
5. A black guinea pig crossed with an albino guinea pig produces 12 black offspring. When the
albino is crossed with a second black one, 7 blacks and 5 albinos are obtained. What is the best
explanation for this genetic situation? Write genotypes for the parents, gametes, and offspring.
In the first situation the Black pig was AA and the albino was aa and that is why all offspring
were black Aa to be exact.
In the second situation the black pig was Aa since we got some offspring as albino
6. You collect two individuals of Drosphila, one a young male and the other a young, unmated
female. Both are normal in appearance, with the red eyes typical of Drosphila. You keep the two
flies in the same bottle, where they mate. Two weeks later, the offspring they have produced all
have red eyes. From the offspring, you select 100 individuals, some male and some female. You
cross each individually with a fly you know to be homozygous for the recessive allele, sepia,
which produces black eyes when homozygous. Examining the results of your 100 crosses, you
observe that in about a half of the crosses, only red-eyed flies were produced. In the other half,
however, the progeny of each cross consists of about 50% red-eyed flies and 50% black-eyed
flies. What were the genotypes of your original two flies?
OMIT