By the way, my homework is due Wednesday, November 13th at 4:10 pm. I would appreciate it if you could please walk me through all of the steps to solve all parts of this problem. Given a genetic map with genes A, B, C, and D, calculate the frequency of the following gametes. The distance between A and B is 25 cM. The distance between B and C is 12 cM. The distance between C and D is 69 cM.
a. a B gamete from a AB/ab genotype
b. A C gametes from a AC/ac genotype
c. Is there another gene between C and D that is not listed on the map?
To solve this problem, we need to understand the concept of genetic mapping and how distances between genes relate to the frequency of different gametes. Let's walk through the steps for each part of the problem:
a. To calculate the frequency of a B gamete from an AB/ab genotype:
1. Start by drawing a genetic map with the given distances between the genes: A - 25 cM - B - 12 cM - C - 69 cM - D.
2. Determine the total map distance between A and B: 25 cM.
3. Divide the distance between A and B by 100 to convert it to the unit of a centiMorgan (cM): 25 cM / 100 = 0.25.
4. Since the AB/ab genotype has one allele for B, there is a 100% chance of passing that allele in the gametes.
5. Therefore, the frequency of a B gamete is 1.
b. To calculate the frequency of an A C gamete from an AC/ac genotype:
1. Using the same genetic map as before, determine the total map distance between A and C: 25 cM + 12 cM = 37 cM.
2. Divide the distance between A and C by 100: 37 cM / 100 = 0.37.
3. Since the AC/ac genotype has one allele for A and one allele for C, there is a 50% chance of passing each of these alleles in the gametes.
4. Multiply the probability of passing the A allele (0.50) by the probability of passing the C allele (0.50) to get the frequency of an AC gamete: 0.50 x 0.50 = 0.25.
5. Therefore, the frequency of an AC gamete is 0.25.
c. To determine if there is another gene between C and D not listed on the map:
1. Look at the genetic map: A - 25 cM - B - 12 cM - C - 69 cM - D.
2. The total map distance between C and D is 69 cM.
3. If there is no other gene between C and D, the total map distance should equal the sum of the distances between each adjacent pair of genes.
4. Calculate the expected total distance between C and D based on the distances between A-B, B-C, and C-D: 25 cM + 12 cM + 69 cM = 106 cM.
5. Compare the expected total distance (106 cM) with the actual total distance (69 cM).
6. If the two distances are different, it indicates that there might be another gene between C and D that is not listed on the map.
7. In this case, there does seem to be a discrepancy between the expected and actual distances, suggesting there might be another gene between C and D. However, without additional information, we cannot provide a definitive answer.
Remember to double-check your calculations and review the given information to ensure accuracy.