BIOL1006 Lecture 14: Lecture 14

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9 Jun 2018

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Lecture 14: Population genetics

The structure of populations

The gene pool

- All alleles, at all loci, in all individuals

- Alleles, not individuals, are the units of selection.

- Specific alleles (genotype) determine survival and reproduction

The Hardy Weinberg Law

‘allele frequencies remain the same from generation to generation unless acted on by a force/

Assumptions:

- Random mating among individuals

- Large population

- No mutation

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Document Summary

All alleles, at all loci, in all individuals. Alleles, not individuals, are the units of selection. Specific alleles (genotype) determine survival and reproduction. Allele frequencies remain the same from generation to generation unless acted on by a force/ Consider two alleles at one locus (a and a) Frequency of the a allele in the gene pool is p. Frequency of a allele in the gene pool is q p + q = 1. So, if 75% (0. 75) of the alleles are at the locus are a, then the remaining 25% (0. 25) of the alleles must be a. Note: we are mixing gametes and alleles from the entire population, not just a single. Calculate the frequency of carriers in a population. Frequency of cystic fibrosis in australia is 1 in 2500 births. Therefore, the frequency of the recessive cf allele is: Example: 10 diseases each at frequency q = 0. 01. P(individual is a carrier for any one = 2pq) = 0. 02.

Related Questions

In a large population of an annual wild pea species, height is controlled by a single locus; DD and Dd individuals are tall, while dd individuals are short. Because the local environment is very windy, tall plants tend to get broken and survive to reproduce only half as well as well as do short plants. Mating is random with respect to height and there is no immigration or emigration. In a population of 21,000 (large enough to be considered infinite for the purposed of the Hardy-Weinberg equilibrium and natural selection models; assume this population size remains constant through the generations described in this question) adult pea plants that successfully reproduce after natural selection through differential survival has occurred, there are 7,000 DD individuals, 7,000 Dd individuals, and 7,000 dd individuals.

a) What will be the frequency of the D allele in the gametes (sperm, in pollen, and ovules) that will unite to make up the next generation?

b) What will be the genotype frequencies of DD, Dd, and dd in the seeds that are formed to start the next generation? How many seeds will there be with each genotype?

c) What will be the genotype frequencies of DD, Dd, and dd in the adults that develop from these seeds and survive to reproduce? How many adults will there be with each genotype?

d) Over a long period of time, what do you expect to happen to the D and d alleles in this population? Why?

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.

indigosnake469

1) Which of these probabilities are NOT independent of eachother?

The probability that a student is a sophomore and has brownhair

The probability that when you roll two dice, you will roll a 6before a 2

The probability that it will rain and the probability ofneeding an umbrella

The probability that there will be heavy traffic on BaltimoreAve and the probability you will lose your cell phone

2) We are defining evolution as a "change in allele frequenciesover time". Ironically, the focus of this lab is the Hardy-Weinbergequilibrium - conditions that, if all met, will result in NOevolution occurring. Which of the following are among theconditions that must be met for the Hardy-Weinberg equilibrium toapply perfectly to a population?

A. The population must be very large

B. Individuals must mate at random

C. The alleles must differ in their effects on survival

D. There must be free migration into and out of thepopulation

A & B

A, B, & C

3)In cats, black fur is dominant over any allele for brown fur.If a homozygous dominant cat makes kittens with a heterozygous cat,what is the probability that the first kitten will have brown fur?Report as a proportion, not percentage, e.g., .1, NOT 10%.

The EGLN1 gene helps regulate body oxygen levels. One allele His dominant over h, and helps increase fitness at high altitude(where oxygen is low). In a study of families in Tibet, researchersfound 422 HH individuals, 377 Hh, and 201 hh individuals. The studyshowed that infant mortality was lower in Hh individuals than hh,and lowest in HH individuals.
Is the Tibetan population in Hardy Weinberg Equilibrium at this H/hgene?

What is the most important factor affecting the strength ofgenetic drift?

The frequency of the rarest genotype

The size of the population

The allele frequencies

The genetic diversity in the population

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BIOL1006 Lecture 14: Lecture 14

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