Thursday, September 20, 2007

Measuring Evolution of Populations

Today, in period 8 and 9, we discussed Measuring Evolution of Populations. We discussed that evolution is the change in allele frequencies in a population. Also something we discussed in this lesson was what would cause allele frequencies not to change. Which include, very large population, no migration, no mutation, random mating, and no natural selection. This is only hypothetically speaking, this would be very hard to accomplish in a realistic population.
Hardy-Weinberg equilibrium was a major part of the lesson today. G.H. Hardy was a mathematician and W. Weinberg was a physician.

G.H. Hardy

W. Weinberg

This does not really exist anywhere, it serves as a model. It is a null hypothesis. This is used to measure if forces are acting on a population; measuring evolutionary change. When counting alleles, the frequency of the dominant allele is represented by p. The frequency of the recessive allele is represented by q. The frequencies of the two alleles must add up to 1 (100%). The equation used to represent this is p + q=1. When you are counting individuals, using the Hardy-Weinberg theorem, the frequency of the:
homozygous dominant: p x q = q²
homozygous recessive: q x q = q²
heterozygotes: (p x q) + (p x q) = 2pq
Like the frequencies of the alleles, all individuals add to 1 (100%). The equation used to represent this is p² + 2pq + q² = 1. These equations can only work, hypothetically, if the population is in Hardy-Weinberg equilibrium.

We also discussed sickle celled anemia.

Sickle cell anemia affects 1 out of 400 African Americans. It is an inheritance of a mutation in gene coding for hemoglobin. Low oxygen levels causes red blood cells to sickle, which then can lead to the clogging of blood vessels;capillaries, if two sickle cells stick together. This can be lethal to younger children, but have a less, but serious effect on older generations. The heterozygotes have an advantage in this case, they are free of both malaria and sickle cell anemia.
The sherpa for tomorrow will be Jackie K.

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