BIOL 1001 Lecture Notes - Lecture 4: January 30, Allele Frequency, Phenotypic Plasticity

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4 Jun 2019

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Allele frequency - hardy weinberg: the abundance of alleles in a population. All the alleles have to add up to 100%. You have to multiply the percentage of the two alleles together if you want to get the frequency of an allele in the population. A1 is represented at 70%, & a2 is represented at 30%. What is the probability of getting a1a1: . 7x. 7= 49% Say you know that 49% of the time there is a a1a1 allele. 7, or 70% so now you know that 70% of the gene pool is a1 alleles. This is the relative frequency of a genotype in a population. So if p= . 7, then q= . 3 you get . 49 + . 42 +. 09 = 1, so 49% are dominant, 42% are heterozygous, and 9% are recessive. The only thing that hardy weinberg requires is 2 alleles, both expressing the same gene.

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Popgen 8: suppose two alleles, C and D, control flower color, CC plants have red flowers, while CD and DD plants have pink flowers. Suppose that in a population of 1000 individuals, I count 840 pink flowered plants. Assuming that the population is in Hardy- Weinberg equilibrium, what is the frequency of the allele C? Correct answer is 0.4 but dont know how to solve for it.

Popgen 9: Popgen 9: Consider a process of one-way migration from a very large population into a small population. A gene has two alleles A1 and A2. The frequency of A1 in the small population (p-small) is 0.3, and the frequency of A1 in the large population (p-large) is 0.8. Assuming a migration rate of m = 0.1, and no mutation, selection, or genetic drift, what do you expect to see in the next generation?

Popgen 14: Recall our model of one-way migration from a large mainland onto a small island. Consider two alleles A1 and A2. The frequency of allele A1 on the mainland (p-mainland) is 0.2, while the frequency of A1 on the island (p-island) is 0.8. The rate of migration from the mainland to the island per generation is 0.1. What is the expected value of p'-island, the frequency of A1 on the island after one generation?

coffeeserval150

Hardy-Weinberg Equilibrium Problems

p is the frequency of the dominant allele in the population

q is the frequency of the recessive allele in the population

p2 is the frequency of the homozygous dominant genotype

q2 is the frequency of the homozygous recessive genotype

2pq is the frequency of the heterozygous genotype

p + q = 1

p2 + 2pq + q2 = 1 Find q2 ï q ï p ï p2 ï 2pq

A rare disorder of cystic fibrosis (characterized by abnormal transport ofchloride and sodium across an epithelium, leading to thick, viscous secretions) occurs every 1 in 3,300 births. To express this trait one must be homozygous recessive (ff).

The cystic fibrosis allele is represented by f. The normal allele is F. Suppose both parents have alleles Ff. The possible combinations of alleles in the children are FF, Ff, Ff and ff. The alleles ff will cause the disease. So, although the parents do not have cystic fibrosis, they can produce children with the disease. The parents are called 'carriers' of the disease

What is the frequency of the population that carries the trait? (Ff)

Q1. What are alleles?Different forms of the same gene.Different genes.The different characteristics of an organism.Genes found only in humans.Q2. If you add up the frequency of homozygotes + the frequency of heterozygotes for one gene (i.e. at one locus) in a population, what number do you get?Q3. People who are heterozygous for the sickle-cell allele:Are susceptible to malaria but not sickle-cell anemia.Are susceptible to sickle-cell anemia but not malaria.Are not susceptible to either sickle-cell anemia or malaria.Are susceptible to both sickle-cecell anemia and malaria.Q4. In the case study in this lab, which genotype is represented by "2pq" in the Hardy-Weinberg equation?Homozygous HbAHomozygous HbSHeterozygous HbA/HbSNo specific genotypeQ5. Suppose that, in an isolated village, the proportion of individuals that have sickle-cell anemia is 0.1 (or 1 of every 10 people). What proportion of the population should be sickle-cell carriers, according to Hardy-Weinberg expectations?Q6. When you simulated the elimination of malaria at the beginning of the lab, once the allele frequencies stabilized, what was the frequency of the HbA allele?Q7. When you investigated regional differences, what was the frequency (over many generations) of the HbS allele in the village in the "slightly wet" part of Africa?Q8. What is the number of deaths due to sickle-cell anemia in a region without mosquitoes expected to be?Very lowVery highModerateRelated to the frequency of malaria allelesQ9. As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time?Because natural selection changes all allele frequencies in populations over time.Because genetic drift causes random fluctuations of allele frequencies in populations.Because diseases will eliminate some of the alleles, generating fluctuations in their frequencies.Because allele frequencies fluctuate before the alleles eventually become fixed.Q10. Imagine a huge population with a gene that has ten functionally equivalent, neutral alleles. A small but genetically representative group of individuals from the big population is transported to an island, forming a small population. Which of the statements below best describes what will likely happen over time, and why?Because natural selection doesn't act on neutral alleles, the frequencies in the two populations should remain the same over time.Genetic drift will cause one allele to first become fixed in the island population, and later to become fixed in the original, large population.Genetic drift will result in the allele frequencies of the two populations diverging over time, with alleles being lost sooner in the island population.The allele frequencies of the two populations will change similarly due to a combination of genetic drift natural selection.

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BIOL 1001 Lecture Notes - Lecture 4: January 30, Allele Frequency, Phenotypic Plasticity

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