BIOB51H3 Lecture Notes - Lecture 9: Punnett Square, Genotype Frequency, Allele Frequency

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14 Oct 2016

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We can discover the luck-free result of combining eggs and sperm to make zygotes by using a punnett square for a mating between an aa female and an aa male. This punnett square predicts that among the offspring of an aa female and an aa male, one-quarter will be aa, one-half aa, and one-quarter aa. We can use the same device to predict the genotypes among the offspring of an entire population. The trick is to write the egg and sperm genotypes along the side and top of the punnett square in proportions that reflect their frequencies in the gene pool. For example, 60% of the eggs carry copies of allele a and 40% carry copies of allele a, so we have written six a"s and four a"s along the side of the square. Likewise, for the sperm, we have written six a"s and four a"s along the top.

Related Questions

1. An animal (called a Box) is diploid, and has 5 types of chromosomes (4 autosomes, 1 pair sex chromosomes). Box sex chromosomes are designated W and Z. Box males are heteromorphic (WZ), and Box females are homomorphic (WW).

Boxes are covered in a thick coat of hair. There is a disease in Box, called hairlessness, that has an inheritance pattern that is W-linked and recessive. The allele used to designate this disease is h. Haired Box are wild-type (allele = h+) and hairless Box are mutant (allele = h). In general (not thinking about Box and hairless) when we say that an inheritance pattern is recessive, we automatically know some things about the genotype of affected/diseased individuals.

A) Is the trait simple, or some other type?

B) Does the presence of one diseased allele cause disease, or are two needed?

C) What other name do we use to describe a heterozygous individual?

In the case of Box and the hairless phenotype, what are all the possible genotypes for a hairless female? What are all the possible genotypes for a hairless male? (You do not need to use complete sentences here)

A heterozygous female is mated with an affected male. Indicate what gametes these two individuals can produce. (You donât need to use complete sentences here)

D) Draw a Punnett square for all the possible offspring that these two Box can create. Place the female gametes across the top of the square, and the male gametes down the left side. Insert a picture of your drawing below.

E) What is the ratio of unaffected to affected female offspring for these parents? For male offspring?

F) Choose one female offspring and one male offspring from the F1 and draw a Punnett Square for a mating between those two individuals (F2). Place the female gametes across the top and the male gametes down the left side. Take a picture of the square and insert it below.

BIOB51H3 Lecture Notes - Lecture 9: Punnett Square, Genotype Frequency, Allele Frequency

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