1. If blood pressure in humans is controlled exclusively by many genes, this wou

Question

1. If blood pressure in humans is controlled exclusively by many genes, this would be an example of a trait. (0.5pt) 2. If blood pressure was not completely due to genetics, and the environment also influenced blood pressure (for example if sleep, diet, exercise, and education also played a role), this would be characterized as a ait. (0.5pt) 3. Let's assume that systolic blood pressure (upper number measured in mm Hg) in humans is a quantitative trait controlled only by 4 genes of equally additive alleles, with a range from 100 mm Hg to 180 mm Hg points. Show your work for full credit! a. Using this information, how many phenotypes are possible for human systolic blood pressure? (0.5pt) b. How many mm Hg does each additive allele contribute? (0.5pt) c. How many additive alleles would an individual with a systolic blood pressure of 130 mm Hg have? (1pt) (1pt) 4. Sex-limited traits: A Are expressed in males OR females but not both B. Are expressed in both sexes only when the character is co-dominant C Are expressed in both sexes only when the character is epistatic D. Are always inherited from the mother E. None of the above Page 1 of 2

Explanation / Answer

Please find the answers below:

Answer 1: Polygenic trait (the traits which are controlled by many genes together are called polygenic traits)

Answer 2: Qantitative inheritance (When environmental factors and other abiotic factors influence the expression of genes and their phenotypes, the mode of inheritance is called quantitative inheritance)

Answer 3:

Part a: Here, the total number of phenotypes possible can be calculated directly by using the formula:

Number of phenotypes= 2n+1, where n is the number of genes.

Since n=4 in this case, we have number of phenotypes as (2*4+1) =9.

Part b: Since the extreme low and high end points here are 100 and 180 i.e. the total difference is 180-100 = 80, each of the 4 genes would contribute to 80/4 or 20 units of pressure.

Part c: In order to have a systolic blood pressure of 130 mm of Hg, two alleles are sufficient for expression since they will contribute to 20 units of pressure each and the maximum pressure would be 140 mm of Hg.

Answer 4: Choice A (Sex-limited traits are those phenotypes which are expressed only in either sexes at a time but never on boths, such as genes responsible for development of breasts in females, spermatogenesis in males etc)

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