Question

Blood pressure in humans is a quantitative trait. Let’s assume the systolic blood pressure (top number) ranges in a population from 80 mm Hg (homozygous recessive genotype) to 220 mm Hg (homozygous dominant genotype) and is controlled by 7 unlinked genes. The alleles of each gene are additive and equal in their effects.

1. The number of additive alleles associated with the minimum (base) phenotype is ________ and the total number of phenotypes possible based solely on genetic influence is _________.

A. 1, 14

B. 1, 15

C. 0, 8

D. 0, 14

E. 0, 15

2. Considering genotype alone, an individual with 5 dominant additive alleles will:

A. Have a systolic blood pressure of 105 mmHg

B. Have a systolic blood pressure of 130 mmHg

C. Have a systolic blood pressure of 200 mmHg

D. Have 2 recessive inert alleles

E. Be homozygous recessive for 2 genes

Please explain why/how you got the answers!! Both apply to the given situation at the beginning.

Answer 1

Solution:

Blood pressure in humans is a quantitative trait. Let's assume the systolic blood pressure (top number) ranges in a population from 80 mm Hg (homozygous recessive genotype) to 220 mm Hg (homozygous dominant genotype) and is controlled by 7 unlinked genes. The alleles of each gene are additive and equal in their effects. 1. The number of additive alleles associated with the minimum (base) phenotype is and the total number of phenotypes possible based solely on genetic influence is _______ A. 1, 14 B. 1. 15 C. O, 8 D. O, 14 E. O, 15 2. Considering genotype alone, an individual with 5 dominant additive alleles will: A. Have a systolic blood pressure of 105 mmHg B. Have a systolic blood pressure of 130 mmHg C. Have a systolic blood pressure of 200 mmHg D. Have 2 recessive inert alleles E. Be homozygous recessive for 2 genes

Explanation:

Note that the phenotype with minimum value will have the genotype with all recessive alleles (aabbccddeeffgg).

• The minimum systolic blood pressure is 80 mmHg and maximum is 220 mm Hg. It is given that there are 7 gene pails, thus maximum number of additive alleles will be 14, as each gene has two alleles. • Contrubution by each additive allele : (Maximum Trait value - Minimum trait value] - Number of alleles = (220-80) 14 = 140 14 = 10. * Let the 7 gene pairs be A, B, C, D, E, F and G. Thus, aabbcodd eeffag will have minimum value (80mmig) and AABBCC DDE EFFGG will have maximum value (220 mmHg). Total phenotypes possible = 1+ total number of additive alleles = 1+ 14 = 15. An individual with 5 additive alleles , will have an extra contribution of 10 units from each , to the minimum value, ie. = (80) + ( 5x10) 80 + 50 130 mm Hg •

Number of phenotypes possible is 15 because, phenotypes will range from no additive allele to a phenotype with 14 additive allele.

Answer 1:(E) 0,15

Answer 2: (B) 130 mmHg