Biology 1201A Lecture Notes - Lecture 13: Genotype Frequency, Genetic Drift, Zygosity

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apricotscorpion868

14 Dec 2019

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All equally likely to survive and reproduce (no selection) Population is infinite in size (no genetic drift) Check to see if population is in hwe. Observed genotype frequencies must match expected p + q = 1 p^2 } genotype. Selection acts on the phenotype, not the genotype. Allele frequencies - dominant allele eliminated from population. Allele frequencies - recessive allele not eliminated from population. Genotype frequencies with recessive phenotype not eliminated - recessive allele maintained in the heterozygote. Very difficult to get rid of the recessive allele. How quickly an allele becomes fixed in a population. Affects amount of variation in a population.

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II think this is a pretty basic Hardy-Weinberg Problem, I justdon;t know how to solve it yet. Thank you for your help!

Assume a population of 800 individuals with the followinggenotypes:452 AA, 296 Aa, and 52 aa. This is the 1stgeneration.

a. Calculate the frequencies for A___ and a___. Do this fromgenotype frequencies (do NOT assume Hardy Weinberg Equilibrium)

b. Use the allele frequencies from part a to calculate theexpected genotype frequencies for AA___ Aa___ and aa__

c. Based on your allele frequencies above, how many of eachgenotype would you expect if the population of 800 people were inHardy-Weinberg Equilibrium? AA____ Aa____aa____

d. Suppose that the original population (452 AA; 296 Aa; 52 aa)experienced an epidemic of an infectious disease that kills 75% ofeach homzygous class ( AA and aa). and 25% of the heterozygotes.How many of each genotype would survive?

e. The results of part e are still the first generation, butpost-epidemic survivors. What are the new allele frequencies?

f. Assume the 1st generation post-epidemic survivors materandomly, and there is no selection, no migration, no mutation, nogenetic drift. What frequency of each genotype is expected in the2nd generation?

g. If the 2nd generation contains 350 indivduals how many ofeach genotype do you expect?

cerisekangaroo944

In 1908 Hardy and Weinberg published papers showing that the binomial or multinomial could be applied in genetics to predict the frequencies of genotypes when allele frequencies where known. The formal algebraic proof of this Hardy-Weinberg Equilibrium Law assumes that there is no mutation in the population. This assumption is necessary, because a. organisms reproduce sexually and litter or family sizes vary. b. populations will exhibit random sampling changes in allele frequency. c. populations are not infinite and the Hardy-Weinberg proof is only a very crude approximation when natural selection is acting. d. populations are not closed and reproduce both sexually and asexually so an infinite size population is required to preserve genetic variation. e. allowing alleles to change would alter their frequencies.

amethystcrab894

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?

Biology 1201A Lecture Notes - Lecture 13: Genotype Frequency, Genetic Drift, Zygosity

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