bioq10 - Zak Murdock Period 1 Video Questions 1) Variation...

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Zak Murdock Period 1 Video Questions 1) Variation in a population is due to mutation and a number of other specific evolutionary agents. Mutation is the origin of genetic variation. A mutation is defined as any change in an organism’s DNA. All mutations of organisms appear to be random with respect to the adaptive needs of the specific organisms. However, most mutations are usually harmful or neutral to the bearer of the mutation. Although if environmental conditions change, previously harmful alleles may actually become an advantage. Mutations can then restore alleles in populations that were once removed by evolution, thus causing a variation in a population. Although most mutations do not help populations, they may indeed both create and help maintain genetic variation within populations. Other than mutation, movement of individuals or gametes, followed by reproduction, produces gene flow, which leads to variation in population. Gene flow is another evolutionary agent that leads to variation in population. Migrations of individuals and movements of gametes between populations are very common. The reproduction of arriving individuals may either add new alleles to the gene pool of the population, or change the frequencies of already present alleles. The addition of new alleles to a population or the change of allele frequencies due to gene flow is a cause in variation of populations. Another evolutionary agent that causes population variation includes genetic drift. Genetic drift is the random loss of individuals and the alleles they possess in a population. This may cause large changes in allele frequencies from one generation to the next, thus causing a variation in the population. During population bottlenecks, periods when normally large populations reduce in size with only a small number of individuals surviving, genetic variation can be greatly reduced. Other than genetic drift causing variation, nonrandom mating is also a factor in variation of a population. Nonrandom mating may cause an overrepresentation of homozygous genotypes or
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This note was uploaded on 04/28/2010 for the course PHYSICS 213 taught by Professor Padamsee during the Spring '10 term at Cornell.

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bioq10 - Zak Murdock Period 1 Video Questions 1) Variation...

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