Genetics

  1. A gene has two alleles. The frequency of the dominant allele is 0.65. What is the frequency of the recessive allele?
  2. Liver is a brown color found in Dalmatian dogs, producing brown spots on the dog instead of the traditional black. Liver is recessive to black, and the frequency of liver in Dalmatians is 21%. What is the frequency of the recessive liver allele in Dalmatians?
  3. The ABO blood group is controlled by three alleles, A, B and O. A and B are codominant, such that if a person inherits one of each they are blood type AB. O is recessive to both A and B. A population of people are genotyped and have the following numbers are counted:

Blood Type Number
AB 6
AO 19
AA 8
BO 23
BB 10
OO 34

What are the frequencies of the A, B and O alleles?
  1. In a large, randomly mating herd of cattle, 16% of the newborn calves have a certain type of dwarfism because of a homozygous recessive allele. What is the frequency of the recessive dwarfism allele?
  2. What is the frequency of heterozygous carriers in the herd?
  3. Rhode Island Red chickens lay, on average, 6 eggs per week. You raise Rhode Island Reds and want to increase egg production in your flock. You select the top 25% of your egg layers to breed – these chickens lay, on average, 8.5 eggs per week. After you breed them and the offspring grow to maturity, the offspring lay, on average, 7.1 eggs per week. What is the heritability of egg laying in Rhode Island Red chickens? Genetics
  4. You are a population geneticist studying a particular disease, which is inherited as an autosomal recessive trait. In the population you are studying, the incidence of the disease is 2%. You need to determine answers to the following questions:

• Calculate the frequency of the normal allele and the disease allele in this population.
• What percentage of your population are carriers for this disease?
• What will be the incidence of this disease in the following generation?
• If this disease is fatal in childhood, what will be the frequency of the normal and disease alleles in the parental generation (breeding adults)?
• If the disease is fatal in childhood, what will be the incidence of the disease in the following generation?

  1. You are a geneticist studying the frequency of coat color alleles in a local rabbit population. Rabbits that carry two dominant alleles of a particular gene (BB) are brown, while 3.5% of the population are homozygous for the recessive allele (bb) and are white. Heterozygotes (Bb) are mottled, a mixture of brown and white. Assuming this population is in HWE, what percentage of rabbits do you expect to be brown, and what percentage do you expect to be mottled?

As it turns out, this population is not in HWE. You sample 1,000 rabbits and find the following:

752 Brown rabbits
210 Mottled rabbits
38 White rabbits

After observing this population, you find that due to their white coloring, 90% of white rabbits die from predation before they can reproduce. Additionally, 50% of mottled rabbits die from predation before reproducing. Given this information, what do you expect the frequencies of brown, mottled and white rabbits to be in the next generation?

Sample Solution

ACED ESSAYS