Question

Draw a chart showing the crossing between red and white flowered pea plants till F2 generation. Find out the genotypic and phenotypic ratio of F2 generation. When the mating of black and white rats takes place, all the offspring produced in first generation are black. Why there are no white rats?

Answer 1

part 1

F1 cross -

RR * rr

Rr, Rr, Rr, Rr

F2 Cross

Rr * Rr

RR, Rr, Rr, rr

Part 2

Black is dominant over white

Step-by-step explanation:

Let the allele for red color trait be R and white color trait be r

Red is dominant over white

Genotype of true breeding parents

Red - RR

white - rr

F1 cross -

RR * rr

Rr, Rr, Rr, Rr

All the offspring are red and of genotype Rr

F2 Cross

Rr * Rr

RR, Rr, Rr, rr

RR: Rr: rr = 1:2:1

Phenotype ration

red (RR, Rr) : white (rr)

3:1

part 2

Black is dominant over white

hence, in first generation cross all mice become white