Snapdragon flowers exhibit incomplete dominance in flower colour such that Rr in

Question

Snapdragon flowers exhibit incomplete dominance in flower colour such that Rr individuals have pink flowers, rr have white flowers, and RR have red flowers. You encounter a population of flowering snapdragon and count 3 individuals with white flowers, 39 individuals with pink flowers, and 8 individuals with red flowers. (Note: the numbers will be changed in your test.)

a. If the population were in Hardy-Weinberg equilibrium, how many pink individuals would you expect to find in a sample of 50 plants?

b. What are two distinct hypotheses (other than population size) that could be used to explain your observation (that is, the difference between what you observe and expect)?

Explanation / Answer

Observed Genotype frequencies:

RR = p2 = 8/50 = 0.16

Rr = 2pq = 39/50= 0.78

rr = q2 = 3/50= 0.06

Allele frequencies:

Frequency of R = p = p2 + 1/2 (2pq) = 0.16 + 1/2 (0.78) = 0.55

Frequency of r= q = 1 - p = 1 - 0.55 = 0.45

Expected Genotype frequencies:

RR = p2 = (0.55)2 = 0.3025

Rr= 2pq = 2 (0.55)(0.45) = 0.495

rr = q2 = (0.45)2 = 0.2025

Expected number of individuals:

RR = 0.3025 (50) = 15

Rr= 0.495 (50) = 25

rr = 0.2025 (50) = 10

X2 = ( 8-15)2 /15 + (39-25)2 /25 + (3-10)2 /10

= 49/15 + 196/25 + 49/10

= 3.27 + 7.84+ 4.9

= 16.01

Because the recessive allele frequency ( q) has changed, the population is NOT in a state of hardy wein equiliribium .25 pink individual were found.

2. no natural selection: all genotypes are equal in viability and fertlity, selection is a reproductive suceess carried to the next generation

no migration ; no allelic and genotype frequencies changed due to loss or addition of alleles through migration of individuals into a population

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