The Old German Baptist Brethren, informally known as Dunkers, is a small religio

Question

The Old German Baptist Brethren, informally known as Dunkers, is a small religious denomination founded in Germany in 1708. Beginning in 1719, a number of Dunkers emigrated from Germany to Pennsylvania. As of 1950, there were about 3500 Dunkers in the United States. Dunkers are not as strict about their lifestyle as other similar relgious groups, such as the Amish. However, Dunkers usally marry within their community and converts to the Dunker denomination are relatively rare.

In 1950, geneticist Bently Glass studied a population of over 200 Dunkers in southern Pennsylvania. Glass used the MN blood group, a blood type conrolled by a single gene with two loci. Individuals may be type M (homozygous for the M allele), N (homozygous for the N allele), or MN (heterozygous). The MN blood type has little clinical significance, and as far as is known there is no survival advantage in having one MN blood type over of the other.

a) Glass found 102 Dunkers with the type M blood, 96 with type MN, and 31 with type N. Calculate the Alle Frequencies.

b) Calculate the expected numbers of people who would have each blood type if the population were in Hardy-Weinberg equilibrium.

c) In Germany today, about 30% of the entire population has type M blood, 50% has type MN, and 20% has type N. In the eastern United States the figures are almost identical (29% M, 50% MN, 21% N). Disucss why both of these sets of allele frequencies might differ from the frequencies in the Dunkers. (There could be many reasons, but restrict yourself to the most likely.)

Explanation / Answer

Hardy-Weinberg equilibrium:
p+q = 1
p2+2pq+q2 = 1

Conditions for H-W equilibrium:
1. A large population
2. Random mating
3. No natural selection
4. No immigration or emigration
5. No change in allelic frequency due to mutation

Total population = 200
Total alleles = 400
Frequency of MM, p2 = 96/200 = 0.48
Frequency of M = 0.692
Frequency of NN, q2 = 31/200 = 0.155
Frequency of N = 0.393
Frequency of Rr, 2pq = 2 X 0.692 X 0.393 = 0.543

The populations may drift from H-W equilibrium because,
1. The US and german population exhibits a large number of immigration and emigration

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