Question

8. In a cross between plants with pink flowers and plants with white flowers the offsprings of F1
generation all had pink flowers. When the F1 generation was self-crossed, it was observed in the
F2 generation that out of 100,75 flowers were pink. Make a cross and answer the following:
1) What is the result of the F1 generation?
ii) What is the ratio of pink: white flowers in the F2 generation?​

Answer 1

Answer:

a)Genotype of F progeny is Pp

b)Ratio of pink:white flowers in F2 generation is 3:1

When a pink and a white flower is crossed they have pair of homozygous alleles that is they are true breedings.

Let the genotype of pink flower is PP

So genotype of white flower is pp

P is dominant over small p that is pink flowers are dominant over white.

a)So when pure breeding lines are crossed the F1 generation has dominant charactor so is pink in colour and F1 is heterozygous that is genotype of F1 is Pp.

Cross between PP *pp----------->F1 =Pp (pink)

Now when F1 is selfed we get F2 generation with 2 heterozygous and two homozygous.

In heterozygyous the dominant one is expressed so they are pink in colour.

The genotypes of F2 are PP Pp Pp and pp so three are pink and one is white.

b)For F2 Pp *Pp------->PP Pp Pp pp

In F2 out of 100 ,75 are pink

So number of white are 100-75=25

Ratio of pink to white is 75:25=3:1