22. A new kind of tulip is produced that develops only purple or pink flowers. A

Question

22. A new kind of tulip 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 tulips from a large cultivated field yields 847 purple flowers, and 153 pink flowers. a. Determine the frequency of the purple and pink alleles in this field population. b. Estimate the proportion of all purple flowering plants that are heterozygotes and homozygotes.

Explanation / Answer

a. In general notation allele frequency for dominant allele is represented by p while for recessive allele is represented by q.

We have to find allele frequency for purple flower (P) and pink flower (p)

It is given that p is recessive allele and pp homozygote condition will result in pink flowers. Thus, the frequency will be given by q2 (for recessive alleles).

Number of pink flowers= 153

Now calculating frequency of genotype pp

q2= 153/1000 = .153

This means q is square root of .153

q= .3911

Therefore, frequency of pink allele = .3911

Calculating the frequency of purple allele

p= 1-q

= 1- .3911

= .6089

Therefore, frequency of purple allele = .6089

b. By using values of allele frequencies p and q, assuming Hardy Weinberg equilibrium genotype frequencies can be calculated as:

PP (p2) = .371

Pp (2pq) = .476

pp (q2) = .153

Using these genotype frequencies the number of heterozygotes among purple coloured flowers is Pp

= .476 * 1000

= 476

Using these genotype frequencies the number of homozygotes among purple coloured flowers is PP

= .371 * 1000

= 371

Therefore, heterozygote purple flowers are 476 while homozygote purple flowers in the population are 371.

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