Question

Which is correct genotypic rotio of mendal dihibrid cross among 1:2:1:2:4:2:1:2:1 and 1:2:2:4:1:2:1:2:1 ?

Answer 1

1:2:2:4:1:2:1:2:1 is the correct genotypic ratio of Mendel's Dihybrid cross

Explanation:

Mendel's dihybrid phenotypic ratio is 9:3:3;:1.

Lets us explain by taking the example of pea plant .
A cross is made between a pure pea plant with yellow colored cotyledons and round seeds with pure pea plant with green colored cotyledons and wrinkled seeds.

Yellow color of cotyledons(Y) is dominant over green color (y).
Round shape of seed (R) is dominant over wrinkled seeds (r).

All the plants in `F1` generation will be having Yellow colored cotyledons and with round seeds.

We get `F2` generation by allowing pollinaton amig plants of `F1` generation. The offsprings in `F2` generation will be yellow round: yellow wrinkled: green round : green wrinkled in ration of 9:3:3:1.

Yellow round pea plants (9) will have 4 types of genotypes:
YYRR (1), YYRr (2), Yy RR (2) and YyRr (4).

Yellow wrinkled (3) will have 2 genotypes:
YYrr (1), Yyrr (2).

Green round (3) will have 2 genotypes:
yyRR (1), yyRr (2)

Green wrinkled (1) will have only one genotype:
yyrr(1).

Thus the F2 dihybrid genotypic ratio will be 1:2:2:4:1:2:1:2:1