Question

In a trihybrid cross, what is the percentage of the offspring omozygous for all three genes?
To solve this, I considered that for each gene half the offspring is omozygous, so I would say (1/2)*(1/2)*(1/2)=1/8. The problem is: when I checked my answer by sketching the Punnet square, I found out that 1/32 of the offspring is omozygous for all three genes. So, what is the right answer? Thanks in advance!

Answer 1

A trihybrid cross is made between two organisms that are heterozygous for three different traits including three genes. Assuming three genes A, B, and C with A allele dominant over a, B allele dominant over b, and C allele dominnat over c. Thus, when a cross is made between organisms heterozygous (AaBbCc and AaBbCc) for these genes, the gametes would be ABC, ABc, AbC, Abc, aBC, aBc, abC, and abc. An example of Punnett square for a trihybrid cross can be referred. This would result in 64 number of offspring. Only two offsrping will be homozygous for all three genes, that is, AABBCC and aabbcc. The ratio would be 2/64 or 1/32.

On the basis of gametes formed and cross, the correct answer is 1/32 or 3.12 % offspring would be homozygous for all three genes in a trihybrid cross.