In domestic cats, orange (O) for is dominant to black (o) and short hair (S) is

ID: 92672 • Letter: I

Question

In domestic cats, orange (O) for is dominant to black (o) and short hair (S) is dominant to long hair (s). Suppose that Desi, a male with a long black coat, mates with Lucille, a female with a short orange coat They have 9 kittens of the following phenotypes: 3 males with short orange fur 2 males with long orange fur 2 females with short coats with patches of black and orange 3 females with long coats with patches of black and orange A. What are the genotypes of Desi and Lucille? If either trait is sex-linked, that should be denoted in the genotype. (Clearly distinguish capital and lowercase letters in your answer!) B. What accounts for the patches of orange and black fur in the female kittens? C. Suppose that one of the orange, short hair males (from above) mates with one of his patched, long hair sisters. What offspring are possible? Give genotypes, phenotypes and expected proportions of each. (Draw a Punnett square or a branch diagram to show the answer.) Consider the autosomal sex-influenced trait of pattern baldness (B'), which is dominant in men and recessive in women. A heterozygous bald (B'B) man marries a heterozygous non-bald (B'B) woman. A. What is the probability among sons that the son will be bald? B. What is the probability among daughters that a daughter will be bald? C. Suppose a female, who has a bald father that is heterozygous for the baldness allele and a mother who does not carry the allele for baldness, marries a bald man with genotype B'B. The couple has a son. What is the probability that the son will be bald as an adult?

Explanation / Answer

Hi,
The genotype of parents are:
Desi = male long black coat = ssoo ( all are recessive)
Lucille = female short orange coat = S_O_ ( _ because even a single dominant allele can give rise to dominant phenotype. The other can be S or s).
The genotype of kitten are possible for each phenotype:
Orange fur = Oo / OO
Black fur = oo
Pathes of black and orange = it is a codominance trait = Oo.
Long hair = ss
Short hair = Ss / SS
A. One of the kitten has long hair ; so her genotype is ss; that means each s is contributed by one parent. Hence the genotype of the parent must be SsO_
None of the kitten has complete black coat = that means no ‘oo’ combination. Hence the genotype of the parent must be SsOO.
But there are no females with orange fur and also no male with black fur. Hence it is a sex linekd trait.
Hence the genotypes are: Desi = male long black coat = ssxoY
Lucille = female short orange coat = SsxOxo

B. The patches of prange and black indicate the co dominance . Both the alleles are present in the organism. When the above parents mate: all female kittens are bon with SsxOxo or ssxOxo genotypes. The presence of the both xO and xo makes the patchy coat.
C. The genotype of the orange, short hair male is = Ss xOy and that of long hair patched female is = ssxOxo. Their gametes are as given in the table.

SsxOxO

short orange

SsxOY

short orange

ssxOxO

long orange

ssxOy

long orange

SsxOxo

short orange

Ssxoy

Short black

ssxOxo

long orange

ssxoY

long black

The final answer is:
Short orange = 3/8
Long orange = 3/8
Short black = 1/8
Long black = 1/8

Cross SxO SY sxO sY sxO

SsxOxO

short orange

SsxOY

short orange

ssxOxO

long orange

ssxOy

long orange

sxo

SsxOxo

short orange

Ssxoy

Short black

ssxOxo

long orange

ssxoY

long black

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