AS 102-Assignment 1

Question 1
A rough-coated guinea pig was crossed
with a smooth-coated guinea pig. All the
F1 offspring were rough-coated. When
the F1 were allowed to interbreed, 135 of
the F2 offspring were rough-coated and
44 had smooth coat. What were the
genotypes of the parental and F1
Question 2
Two black female mice (M and N) were
crossed with the same brown male. In a
number of litters female M produced 9
black and 7 brown offspring. Female N
produced 14 black offspring. What is the
mechanism of inheritance of black and
brown coat colour in mice? What are the
genotypes of the parents (i.e. M, N and
the male).
Question 3
In chickens the white plumage colour is
dominant to coloured plumage, feathered
shanks are dominant over clean shanks and
pea comb is dominant over single comb. Each
of the gene pairs segregate independently. If a
homozygous white , feathered, pea-combed
hen is crossed with a homozygous coloured,
clean, single-combed cock and the F1
offspring are allowed to interbreed, what
proportion of the birds in the F2 will be
coloured, feathered and pea-combed?
Question 4
In guinea pigs, short hair (L) is dominant to
long hair (l), and the heterozygous conditions
of yellow (CY) and white coat (CW) gives cream
coat. A short-haired, cream guinea pig is bred
to a long-haired, white guinea pig, and a longhaired, cream guinea pig offspring is produced.
When the offspring grows up, it is bred back to
the short-haired, cream parent. What
phenotypic classes and in what proportions are
expected among the F2 offspring?
Question 5
In poultry the dominant alleles for rose comb
(R) and pea comb (P), if present together,
produce walnut comb. The recessive alleles of
each gene, when present together in a
homozygous state, give single comb. A rosecombed hen was crossed with a walnut
combed cock and produced offspring of which
3/8 were walnut, 3/8 rose, 1/8 pea and 1/8
single. Determine the genotypes of the two
Question 6
In dogs the dominant allele S causes solid
coat colour while the recessive allele s results
in white spots on a coloured background. The
black coat colour allele B is dominant to the
brown allele b, but these genes are expressed
only in the presence of the genotype a/a.
Individuals that are A/- are yellow regardless of
B alleles. When a solid yellow male was mated
to a solid brown female six pups were
produced. They are phenotypes were: 2 solid
black, 1 spotted yellow, 1 spotted black and 2
solid brown. What were the genotypes of the
male and female parents?
Question 7
In sheep, white hair (W) is dominant over
black hair (w). Horned (H) is dominant
over hornless (h) in males but recessive
in females. If a homozygous horned
white ram is bred to a homozygous
hornless black ewe, what will be the
appearance of the F1 and the F2
Question 8
• In Drosophila, white eyes are a sex-linked
characters. The mutant allele for white
eyes (w) is recessive to the wild-type allele
for brick-red eye colour (w+). A white-eyed
female is crossed with a red-eyed male.
An F1 female from this cross is mated with
her father, and an F1 male is mated with
his mother. What will be the eye colour of
the offspring of these last two crosses?
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