What are two processes through which genetic drift can occur?

Answer 1

Bottleneck effect: the reduction in the number of organisms

and Founders effect: the migration of a few individuals to a new area.

:)

Answer 2

Random events in small populations and the founder effect. The first can be just about any thing, but the second is about the emigration of a part of a population to another area/population. These emigrants are not fully representative of the parent populations allele frequency; hence drift.

Other causes of genetic drift:

1- Changes in allele frequency: Sometimes, there can be random fluctuations in the numbers of alleles in a population. These changes in relative allele frequency, called genetic drift, can either increase or decrease by chance over time.Typically, genetic drift occurs in small populations, where infrequently-occurring alleles face a greater chance of being lost.

2- population bottleneck : Genetic drift is common after a population experiences a population bottleneck. A population bottleneck arises when a significant number of individuals in a population die or are otherwise prevented from breeding, resulting in a drastic decrease in the size of the population.

3-Distribution: How does the physical distribution of individuals affect a population? A species with a broad distribution rarely has the same genetic makeup over its entire range. For example, individuals in a population living at one end of the range may live at a higher altitude and encounter different climatic conditions than others living at the opposite end at a lower altitude.

4- Migration: Migration is the movement of organisms from one location to another. Although it can occur in cyclical patterns (as it does in birds), migration when used in a population genetics context often refers to the movement of individuals into or out of a defined population.

5-Random chance

Answer 3

Genetic drift is the fluctuation of allele frequencies in a population due to chance. Chance plays a role in several ways. Copies of alleles can be lost because they never make it into gametes. Another possibility is, if the allele copy makes into a sperm, that sperm isn't the one that fertilizes an egg. Maybe the organism that carries copies of the allele in its gametes fails to find a mate, or is killed before reproducing. These kinds of events can influence the frequency of that alelle in a population, and occurs regardless of any selection for or against that allele. Obviously, the smaller the population, the larger the effect drift has on the allele frequency. For example, consider a population of four organisms. Each has two copies of a particular gene (one on each chromosome). Now, consider a mutation that creates a new allele for that gene, and that it appears on one chromosome of one individual. That allele will have a frequency of 1/8 in that population, so if it is lost, the frequency change will be 1/8. Now imagine a population of eight individuals; the frequency of the new allele would be 1/16, so if it was lost, the change in frequency would be less than in a population of four. It should therefore be easy to see that the effect of genetic drift on allelic frequency change is dramatically less in very large populations. In fact, in an essentially infinite population, genetic drift would have a negligible effect on the frequency of an allele. Another factor that can influence allele frequency, and which is a part of genetic drift is non-random mating. If an organism does not have an equal probability of mating with any other organism in a population, then some alleles will increase or decrease in frequency simply due to that. For instance, if a population exists over a large geographic range, individuals that live closer to each other have a greater probability of mating than those who live far apart. Species who employ reproductive strategies such as leks,where males gather together and compete for the privilege of mating with females are also examples of non-random mating. Lekking increases the effects of drift because it reduces what biologists call the effective population size, or the number of breeding adults. For the above reasons, when population geneticists want to study factors that affect the frequency of an allele (such as natural selection), and they want to minimize the effects of drift, they model populations that are very large (essentially infinite) and assume random mating.

Answer 4

Genetic drift can occur through the founder effect, which happens when a small group of individuals establishes a new population that is genetically different from the original population. It can also occur through the bottleneck effect, where a sharp reduction in population size leads to a loss of genetic diversity due to random sampling of alleles.

Answer 5

Bottleneck Effect & Founder Effect

Answer 6

loss of genetic diversity

Answer 7

Founder Effect and Bottleneck Effect