5) We have considered three processes that influence allele frequency: natural s

Question

5) We have considered three processes that influence allele frequency: natural selection, mutation, and random drift. To these we can add migration ("gene flow') see Sec. 7.1 in the book. How does each of these processes affect the amount of genetic variation within populations in the long run? Is there any process that can sometimes increase variation, and sometimes decrease it? Explain 6) In this problem, you will use a computer program written by one of the textbook authors to examine the interaction between natural selection and random drift. First, download the program ("AlleleA1") from the following link: ht facu There are different versions for Mac and PC-see instructions on the web page). Then follow the instructions below to use the program to compare what happens to a slightly advantageous allele (Ar in this case) in large and small populations Set the initial frequency of the AI allele to 0.5, and enter fitness values of 1,0.99, and 0.98 for AIAI, AIA2,and A2A2, respectively. Keep the values for mutation rates, migration fraction, and inbreeding coefficient at 0, the default. Click on the X-axis to set the number of generations to 1,000. Then run at least 10 simulations for each of the population sizes below, recording the number of times that each allele fixes for each population size of times A2 fixes Population size of times A1 fixes of times neither fixes 100 500 "this is unlikely to happen if you run the simulations for 1000 generations, but I've included the column just in case. Based on the results, what can you conclude about how effective natural selection is in small vs. large populations? What implications does this have for the long term survival prospects of small populations?

Explanation / Answer

Ans:

processes that affect the amount of genetic variations within populations are:

1.Natural selection

2.Mutation

3.Random drift

Explanation:

1.Natural selection:is a theory that states that those individuals who are best adapted to live in area will survive and reproduce.Within a given population,there exists a normal degree of genetic variation that may or may not make an individual more adapted to environment.

2.Mutation:means changes in the sequence of DNA.However,some mutations result in beneficial effects,some result in deleterious effect.Mutations lead to genetic variation by producing random changes in population.

3.Random drift:Sometimes there can be random fluctuations in the no of alleles in the population.These changes in relative allele frequency is called random drift or genetic drift.Random drift can also cause new population to be distinct from its original popuation.Thus,play role in evolution of new species.

Processes that can sometimes increase or decrease variation:

1.processes that can increase genetic variation:Mutation,Recombination and Gene flow.

2.processes that can decrease genetic variation:Genetic drift and Natural selection.

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