Multiple Choice
Which of the following is an example of a trait that could be present in a newt population as described in studies of genetic variance?
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20. Quantitative Genetics
Traits and Variance
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A trait controlled through polygenic inheritance was observed in a series of experiments. A brown eyed rabbit was mated with a blue eyed rabbit. 130 F2 offspring were produced. 2 offspring had brown eyes and 2 offspring had blue eyes. How many polygenes control eye color in rabbits?
A
1
B
2
C
3
D
4
Verified step by step guidance1
Understand that polygenic inheritance involves multiple genes (polygenes) contributing to a single trait, such as eye color in rabbits.
Recognize that the distribution of phenotypes in the F2 generation can provide clues about the number of polygenes involved. In this case, the extreme phenotypes (brown and blue eyes) are rare.
Recall that the number of phenotypic classes in polygenic inheritance is given by the formula: number of phenotypic classes = 2n + 1, where n is the number of polygenes.
Given that there are 2 offspring with brown eyes and 2 with blue eyes, these represent the extreme phenotypes. The rest of the offspring will have intermediate eye colors.
Use the formula to determine the number of polygenes: if there are 2 extreme phenotypes, then 2n + 1 = 5 phenotypic classes, which implies n = 2. Therefore, 3 polygenes control the eye color in rabbits.
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