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Chapter 24: Section 4 (Genetic Drift)

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Siddarth Santhebennur

on 15 April 2011

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Transcript of Chapter 24: Section 4 (Genetic Drift)

Genetic Drift What is Genetic Drift? The random change in population’s allele frequencies from one generation to the next that is attributable to change.
The term was coined by Mr. Sewall Wright Populations Genetic Drift all depends on the SIZE of the population
....BUT WHY?? Genetic Drift favors either the elimination or fixation of an allele.
Small Populations have much higer random sampling error (random chance)
compared to larger populations:
Chance is the key factor which determines what road the allele will take in small populations Larger Populations have a low random sampling error You guys paying attention to my beautiful prezi? Gene Pool: all of the alleles for every gene in a given population Population: a group of individuals of the same species that occupy the same environment and can be interbreed Genetic drift has the ability to rapidly alter allele frequencies when population THE BOTTLENECK EFFECT A situation in which a population size is dramatically reduced and then rebounds. While the population is small, genetic drift may rapidly reduce the genetic diversity of the population
1.Members may have different allele frequencies that differ from those from the original population
2.Acts quicker to reduce genetic variation when the population size is small. Alleles may be eliminated
3.Eventually the size of population does grow back but variation does not grow along with it The Founder Effect Genetic drift that occurs when a small group of individuals separates from a larger population and establishes a colony in a new location.
Expected to have less genetic variation than original population
Allele frequencies may differ from those of the original population FUN FACT!
This may be known to some of my fellow Spanish III classmates. We recently had a chapter that mentioned this animal as an endangered species....know what I am talking about? My Brother from another mother: Mr. Kimura proposed that change in genetic variation is cased by Genetic Drift....NOT Natural Selection He was a Japanese Evolutionary Biologist
Had many theories & ideas about what actually contributed to evolution in various species
Hated Darwin's ideas....not really. He had something else in mind Mr. Kimura believed in Neutral Variation

Neutral Variation: Genetic variation in which natural selection does not favor any particular genotypeThis DOES NOT affect reproductive success Kimura created the Neutral Theory of Evolution:

States that most genetic variation is due to the accumulation of neutral mutations that have attained high frequencies in a population via genetic drift
Do you know what Neutral Mutations are? Non-Darwinian Theory:
The idea that much of the modern variation in gene sequences is explained by neutral variation rather than adaptive variation. Mr. Kimura did agree with Darwin that Natural Selection is responsible for adaptive changes
He wanted to get the idea across that variation in DNA sequences (due to nuetral mutations) was explained by Neutral Variation Thank You Very Much!
Hope You learned something new from..... h Santhebennur
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