In domestic cats, coat color is an X-linked trait where the allele for black fur (X^B) and… — JAMB UTME

In domestic cats, coat color is an X-linked trait where the allele for black fur ( $X^B$ ) and the allele for orange fur ( $X^O$ ) are codominant, with heterozygous females ( $X^B X^O$ ) exhibiting a tortoiseshell phenotype. If an orange male cat ( $X^O Y$ ) is mated with a tortoiseshell female cat ( $X^B X^O$ ), what percentage of their male offspring is expected to have orange fur?

Cevap: 50 %

Cevap

50%

The female parent (

X^B X^O

) transmits her

X^B

allele or her

X^O

allele to male offspring with equal probability (50% each). Because male offspring inherit the Y chromosome from their father, half of the male offspring will inherit

X^O

and have orange fur (

X^O Y

), giving an expected percentage of 50%.

Adım Adım Çözüm

Determine the gametes produced by each parent

The male parent (

X^O Y

) produces

X^O

and

Y

gametic types in equal proportion (1:1). The female parent (

X^B X^O

) produces

X^B

and

X^O

gametic types in equal proportion (1:1).

Segregation of chromosomes during meiosis separates alleles into gametes.

Determine the genotypes specifically for male offspring

Male offspring inherit the

Y

chromosome from the male parent and one

X

chromosome from the female parent. The possible male genotypes are

X^B Y

(black fur) and

X^O Y

(orange fur).

Sex determination follows the XX-XY system where male sex is determined by inheriting the paternal Y chromosome.

Calculate the percentage of orange males among total male offspring

Out of 2 possible male genotypes (

X^B Y

and

X^O Y

), 1 is orange (

X^O Y

). The ratio is 1 out of 2, which equals 50%.

The question asks for the proportion strictly within male offspring.

Anahtar Kavram

Sex-linked codominant inheritance and sex determination in XX-XY systems

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