Question

Assume that three loci, each with two alleles (A and a, B and b, C and c), determine the difference in height between two homozygous strains of a plant. These genes are additive and equal in their effects on plant height. One strain (aa bb cc) is 10 cm in height. The other strain (AA BB CC) is 22 cm in height. The two strains are crossed, and the resulting F₁ are interbred to produce F₂ progeny. Give the phenotypes and the expected proportions of the F₂ progeny.

***Please show your work***

Answer 1

The height of dominant strain (AABBCC) is 22 cm which is 12 cm more than the recessive strain (aabbcc ). Thus there is an addition of 2 cm in height above the given baseline by each dominant allele. This means that if we look at F1 genotype (AaBbCc) with current baseline and addition of every dominant allele we get it will be 10+6=16 cm in height. So, the proportions and phenotypes in F2 progeny (AaBbCc X AaBbCc) will be as follows:

No. of dominant alleles	Height	F2 progeny proportion
6	22	1/64
5	20	6/64
4	18	15/64
3	16	20/64
2	14	15/64
1	12	6/64
0	10	1/64
		Total= 64/64