Question

In an organism punk is a sex-linked recessive trait and black hair heterozygous female is mated to the white male which is not spotted, the phenotypic ratio of the offspring would be:
A. 1/4 spotted black; 1/4 pink spotted white: 1/4 unspotted black; 1/4 unspotted white
B. 1/2 spotted black: 1/2 pink spotted white
C. 3/4 pink spotted black; 1/4 pink spotted white
D. 3/4 unspotted black; 1/4 pink spotted white

Answer 1

This is a general type of dihybrid cross related questions which were discovered by the genetical scientists named gregor Johan Mendel. This dihybrid cross is specified about the offspring produced by crossing between two homozygous/heterozygous parents. After the cross, it indicates the phenotypic as well as the genotypic character of the offspring.

Complete answer:
Here it is a mathematical hybrid cross which is done by Mendel. In which,

The pink spot is a sex-linked recessive trait, which means that the trait is expressed if it is present in homozygous condition only.
Let allele B be denoted as black colour and r denote pink spot.
Pink spotted black hair heterozygous female is = Bbrr
Not spotted white hair male is = bbRr
Parents: Bbrr X bbRr
Gametes are Br, br. & bR, br

| Br| br
---|---|---
br| BbrrBlack pink spotted| bbrrWhite pink spotted
bR| BbRrBlack unspotted| bbRrWhite unspotted

This implies that the phenotypic ratio of the offspring produced are-
1/4 black unspotted, 1/4 Black pink spotted, 1/4 white pink spotted.
Hence, the correct answer is option (A).

Additional information:
Sex-linked inheritance
A particularly vital class of genetic linkage needs to do with the X and Y sex chromosomes. These not solely carry the genes that verify male and feminine traits however additionally those for a few alternative characteristics furthermore. Genes that area unit carried by either chromosome area unit aid to be sex coupled.
Sex cell inheritance pattern for male/ female kids drawing of chromosome inheritance patterns for male and feminine kids sex chromosome recessive traits that don't seem to be associated with feminine body characteristics area unit primarily expressed within the discernible characteristics.
In women, a recessive allelomorph on one sex chromosome is commonly disguised in their constitution by a dominant traditional allelomorph on the opposite.

Note: Mendel dihybrid cross indicates the offspring character that to its pattern because the character is influenced by the sex linkage. So after the cross, all characters may be present or absent according to its zygosity or dominant and recessive gene which presents in parental character. So all characters are responsible for the parent.