Question

You are studying two isolated populations of birds living on two different islands. In particular, you are interested in studying two different traits in these birds: beak size and feather color.

Beak size is determined by a single gene exhibiting incomplete dominance. Birds with 2 copies of the A allele (genotype AA) have large beaks, birds with 1 copy of the A allele (genotype Aa) have medium beaks, and birds with no copies of the A allele (genotype aa) have small beaks.

Feather color is determined by a different gene. Birds with 1 or 2 copies of the B allele (genotype BB or Bb) are red, and birds with no copies of the B allele (genotype bb) are white.

On island 1 there is a population of 1,000 birds. In that population, the frequency of the A allele is 20%. All of the birds on island 1 are white.

On island 2 there is a population of 3,500 birds. In that population, the frequency of the B allele is 70%. All of the birds on island 2 have small beaks.

In your initial populations on each island, mating is random and the population is in Hardy-Weinberg equilibrium. Use this information to answer the following questions.

Question 4

On island 1, how many birds have medium sized beaks?

a.

0

b.

40

c.

320

d.

500

e.

640

On island 1, a natural disaster strikes, diminishing the supply of large seeds available to birds. Small-beaked birds are still able to find food because they can find small seeds to eat in tight spaces. However, large-beaked and medium-beaked birds suffer from decreased access to food. As a result, 60% of the large-beaked birds die, while 20% of the medium-beaked birds die and only 5% of the small-beaked birds die.

Question 5

How many large-beaked birds survive on island 1 after the natural disaster hits?

a.

16

b.

40

c.

256

d.

320

e.

640

f.

None of the above

After the natural disaster strikes, what is the frequency of the A allele in the surviving population?

a.

16%

b.

20%

c.

44%

d.

84%

e.

None of the above

Question 7

Question text

After the natural disaster strikes, you observe the population over one generation of mating. You notice that mating in this new population is still random, and there is no longer a selective pressure on bird beak sizes. When you count 1000 progeny, how many large-beaked birds do you expect to find?

a.

16

b.

27

c.

164

d.

256

e.

None of the above

Question 8

To avoid dying off in the case of another natural disaster, 200 medium-beaked birds from island 1 migrate to island 2, where there is plenty of food for them and less competition for larger seeds. These birds randomly mate with the original population from island 2. After 1 generation of random mating between these migrant birds and the original population of island 2, you return to the island and count 1000 progeny. How many red birds would you expect to find?

a.

338

b.

490

c.

662

d.

543

e.

690

f.

None of the above

Answer 1

In population genetics, the Hardy–Weinberg principle, also known as the Hardy–Weinberg equilibrium, model, theorem, or law, states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.

In the simplest case of a single locus with two alleles denoted A and a with frequencies f(A) = p and f(a) = q, respectively, the expected genotype frequencies under random mating are f(AA) = p² for the AA homozygotes, f(aa) = q² for the aa homozygotes, and f(Aa) = 2pq for the heterozygotes.

The sum of the entries is p² + 2pq + q² = 1, as the genotype frequencies must sum to one.

Note again that as p + q = 1, the binomial expansion of (p + q)² = p² + 2pq + q² = 1 gives the same relationships.

Q4. Answer:- 320

Explanation:- As it has given that the frequency of allele A is 20% i.e 0.2 (p), so the value of q would be 1-0.2=0.8 (p+q=1) i.e frequency of allele a

So the frequency of medium size beak (genotype is Aa) = 2pq = 2×0.2×0.8= 0.32 i.e 32%

So the number of medium size beak population in a 1000 population would be 320 (32% of 1000).

Q5. Answer:- a) 16

Before disaster the population of large beaked bird was 0.04% i.e 40 . After disaster 60% dies, so remain would be 16

Q6. Answer:-