A new kind of rose is produced that develops only purple or pink flowers. Assume

Question

A new kind of rose is produced that develops only purple or pink flowers. Assume that flower color is controlled by a single-gene locus, and that the purple allele (C) is dominant to the pink allele (c). A random sample of 1000 roses from a large cultivated field yields 212 purple flowers and 788 pink flowers.

If the population is in H-W equilibrium, how many of the plants have genotype Cc?

A new kind of rose is produced that develops only purple or pink flowers. Assume that flower color is controlled by a single-gene locus, and that the purple allele (C) is dominant to the pink allele (c). A random sample of 1000 roses from a large cultivated field yields 212 purple flowers and 788 pink flowers.

If the population is in H-W equilibrium, how many of the plants have genotype Cc?

Explanation / Answer

Answer: 196 (As explained below)

Number of cc individuals = 788, therefore the frequency of the genotype cc (q2) is 788 / 1000 = 0.788.

From this, we can estimate q as:

q = square root of q2 = square root of 0.788 = 0.89

The allele frequency of C is:

p = 1 - q = 1 - 0.89 = 0.11

Assuming HWE, genotype frequencies are as follows:

CC = p2 = 0.012

Cc = 2pq = 2(0.11) (0.89) = 0.1958

cc = q2 = 0.788

Using the expected genotype frequencies, the number Cc is:

2pq (1000) = (0.1958)(1000) = 195.8 = 196.

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