Question

A tetrahybrid plant AaBbCcDd is self-pollinated. How many different types of gametes will be produced by the plant? What is the probability that an offspring will have the dominant phenotype for all four loci?

Answer 1

Part 1: The no of different gamets produced = 2ⁿ , where n is the no. of heterozygous alleles.

In AaBbCbDd genotype the no of heterozygous allele is 4. So, n=4

Thus the of different gamets produced= 2⁴= 16.

Part 2: The genotypes that will be dominant in all 4 loci will be the following:

AaBbCcDd

AABBCCDD

Now if we think the self hybridization of as 4 monohybrid crosses for each of 4 loci, then in each cross the probability of producing offspring with dominant phenotype (either AA or Aa) in each locus is 3/4. So for all the 4 crosses the cumulative probability of producing offspring with dominant phenotype in all four locus is

(3/4)⁴= 81/256= 0.32