Question

Assume you are studying some species of flower that comes in three different colors: red, pink, and white. You know that color is determined by a single locus with two alleles with incomplete dominance. You count 124 red flowers, 62 pink flowers, and 30 white flowers. What are the allele frequencies and is the population in Hardy-Weinberg equilibrium? Calculate the chi squared test statistic and p-value.

Answer 1

Estimation of allele frequencies :

Phenotype	Genotype	Freequency	Allele R	Allele r	Total
Red	RR	124	248	0	248
Pink	Rr	62	62	62	124
White	rr	30	0	60	60
Total	Total	216	310	122	432

Allele R	= 310 / 432	= 0.72
Allele r	= 122 / 432	= 0.28

Expected frequencies =

Red	RR	= 0.72 *0.72 = 0.515	*216 = 111
Pink	Rr	= 2 * 0.72 * 0.28 = 0.405	*216 = 88
White	rr	= 0.28 *0.28 = 0.080	*216 = 17

Null hypothesis: The observed values are not deviating from the expected values.

Category	RR	Rr	rr
Observed values	124	62	30
Exprected Values	111	88	17
Deviation	13	-26	13
D^2	163.1533	652.6133	163.1533
D^2/E	1.47	7.45	9.47	18.39
X^2	18.39
Degrees of freedom	1

Inference: The calculated chisquare value i.e. 18.39 is greater than the table value i.e. 3.84 at 1 DF and 0.05 probability, hence the null hypothesis is rejected which means the popuation is not in HW equilibrium.