Question

Use the information presented below to answer questions 1a – 1e. Please note the information placed between the questions to help you develop your answers.

The feathers of budgies on an isolated tropical island were found to be white, yellow, blue or green. A geneticist studying the inheritance of feather color in budgies discovered that matings between white budgies always produced white feathered birds. However, matings between white feathered birds and yellow or blue feathered birds always produced progeny that were yellow or blue feathered respectively. The geneticist also noted that when yellow birds were mated to blue birds, green feathered progeny were generated.

1. a What is the relationship between alleles controlling feather color in budgies? (4 pts)

2. b How many alleles control feather color in budgies? (1 pt)
3. c If the budgie population on the island is in Hardy-Weinberg equilibrium, write an equation that describes the relationship between the relative frequencies of different genotypes in the population. (2 pt)
4. d After counting the birds on the island the geneticist discovered that 12 out of every 1000 birds counted had white feathers and 240 had yellow feathers. Determine the frequency of each allele controlling feather color in the budgie population on the island. All formulas and calculations must be shown to receive full points (11 pts)
5. e how many birds out of 1000 are expected to have green feathers? (2 pts)

Answer 1

a.White budgies crossed give rise to white only. no other color. But white crossed with either yellow or blue produce either yellow or blue. Which means, white is recessive to yellow as well as blue. That is why both the cases we get yellow or blue colors. When yellow and blue are crossed we are getting, green color. Green is intermediate between yellow and blue. This shows that the blue allele and yellow allele are incompletely dominant. When the two alleles are together an intermediate is obtained.

b.So, the number of alleles involved here for the color are 3. White is recessive to all the others. Blue and yellow are dominant to white. But blue and yellow are incompletely dominant to one another.

c. Hardy-Weinberg equation for the three alleles in the population:

(p+q+r)^2= p^2+q^2+r^2+2pq+2qr+2pr

d.

e. Green feather birds frequency=2pq= 2 X 0.748 x 0.24=0.359

Green feather individuals=0.359 x 1000=359