3. Height in humans is controlled by the additive action of genes and environmen
ID: 68755 • Letter: 3
Question
3. Height in humans is controlled by the additive action of genes and environmental factors. For the purposes of this problem, assume that height is controlled by four genes: A, B, C, and D, and that there are no environmental effects. Assume further that dominant additive alleles contribute two units of height, and recessive alleles contribute one unit of height. Given these assumptions, can two individuals of intermediate height have offspring that are much taller and much shorter than either parent? If so, how can this happen? Show genotypes of parents and offspring to confirm your answer.
Explanation / Answer
Height controlling gene : A, B, C and D
Tall genotypes : AA, BB, CC and DD
Short genotypes : aa, bb, cc and dd
intermediate height genotypes: Aa, Bb, Cc and Dd.
Cross between 2 intermediate height genotypes : Aa X Bb
male/ female
A
a
B
AB
aB
b
Ab
ab
AB: Tall offspring
aB and Ab : intermediate height offspring
ab: Short offspring.
Thus cross between parents of intermediate height produce one tall, two intermediate height offspring and one short offspring.
male/ female
A
a
B
AB
aB
b
Ab
ab
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