question_answer

The total number of progeny obtained from a dihybrid cross is 1280 is F2 generation. How many of them are recombinant type?

A)  240                                       

B)  360

C)  400                                       

D)  720

Correct Answer: C

Solution :

                 A cross yielded dihybrids and at a time consider two pairs of contrasting characters is known as dihybrid cross. The phenotype and genotype of Ty, generation of a dihybrid cross between pea plants with yellow round and green wrinkled seeds.

Number of Individuals	Genotype Class	Phenotype Class
1 2 2 4 1 2 1 2 1	YYRR YY Rr, YY Rr Yy RR, Yy  RR, Yy Rr, Yy Rr YYrr YY rr, Yy Rr yy rr yy rr, yy rR yy rr	Homozygous Yellow round Heterozygous Yellow round
		Yellow round = 9
		Homozygous yellow Wrinkled Heterozygous yellow wrinkled
		Yellow wrinkled = 3
		Homozygous green round Heterozygous green round
		Green round = 3
		Homozygous green wrinkled
		Green wrinkled = 1
16	-	: 3 : 3 : 1

Recombinant types are\[YY\text{ }Rr,\text{ }Yy\text{ }RR,\text{ }Yy\text{ }Rr,\text{ }Yy\text{ }rr,\text{ }yy\text{ }Rr\].i.e., Recombinant type progeny are                 \[\frac{1280\times 5}{16}=400\]