Ina cross between plants with pink flowers and plant with white flowers the offspring of F1 generation all had pink flowers. When the F1 generation was self crossed it was observed in the F2generation that out of 100,75 were pink, make a cross and answer the following
a) what are the genotype of F1 progeny ?
b) what is the ratio of pink : white flowers in the F2 generation?
Answers
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
a) The genotype of F1 progeny is Ww
b) The ratio of pink : white flowers in the F2 generation is 3 : 1
Explanation:
The pink and white flowers are true breedings because they have pair of homozygous alleles.
The genotype of pink flower be WW (dominant character).
The genotype of white flower be ww (recessive character).
Thus, when the true breedings are crossed which means when the pink and the white flowers are crossed, they form heterozygous.
Since, WW is dominant over ww genes, the genotype of F1 progeny is Ww which is pink in colour.
When the progeny is crossed, then it forms 2 homozygous and 2 heterozygous.
Thus, the genotype of the formed plants are WW, Ww, Ww, ww.
WW, Ww and Ww = Pink coloured flowers
ww = White coloured flower