Question

You are studying a disorder that is based on the genetic composition at three loci. Assume that a dominant allele at any locus adds 6 units of risk for the disorder and that a recessive allele at any locus adds 2 units of risk for the disorder. Individuals with 29 or more units of risk develop the disorder. The environment does not affect the presence or absence of this disorder.How many risk units will be present in an individual of genotype AABbCc?

Answer 1

Answer:

28 risk units

Explanation:

This is a classic case of quantitative genetics. The trait is not controlled discretely by dominant and recessive allele and rather shows a "continuous" effect. Such a trait is usually controlled by multiple genes. Each allele adds something to the trait and contribution by dominant allele is more than the contribution by recessive allele.

Here, dominant allele adds 6 units of risk and recessive allele adds 2 units of risk for the disorder. Three genes control the disorder phenotype. An individual with AABbCc genotype has four dominant alleles (AABC) and two recessive alleles (bc) hence the total risk units for this person will be:

(4 *6) + (2*2) = 24 + 4 = 28 units