Question

Three characteristics assort independently in one species of insect: Red eyes (R) are dominant to black eyes (r). Blue wings (B) are dominant to white wings (b). Green bodies (G) are dominant to yellow bodies (g). A cross is made between two heterozygous insects (RrBbGg). What is the probability that the offspring will be homozygous dominant for all three characteristics?

Answer 1

The probability that the offspring will be homozygous dominant for all three characteristics is 1/64.

Step-by-step explanation:

In a three-hybrid cross, three traits are considered. Each parent gives one allele for each trait. When a cross between two heterozygote individuals is made, there are 64 spaces in the punnet square to be filled. Polihybrids produce as many different gametes as different combinations can be formed. The probability that the offspring will be homozygous dominant for all three characteristics is 1/64.

In these crosses 8 gametes intervene, giving place to 27 different genotypes and 8 different phenotypes.

The genotypic proportion is then1:2:2:4:2:4:4:8:1:2:2:4:1:2:2:4:1:2:1:2:2:4:1:2:1:2:1.

And the phenotypic proportion is 27: 9:9:9:3:3:3:1.