Sarah Cope -Genetic Drift

Sarah Cope is a junior at Olathe North High. she plays the violin and loves theater, when she grows up she wishes to be a orchestra teacher, or a acting teacher if orchestra doesn't work out.


Genetic drift—along with natural selection, mutation, and migration—is one of the basic mechanisms of evolution.

In each generation, some individuals may, just by chance, leave behind a few more descendents than other individuals. The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or stronger individuals. That, is genetic drift. It happens to ALL populations—there’s no avoiding the vagaries of chance.

Sometimes genetic drift can be useful at times such as increaseing the inbreeding coefficient and homozygosity, but in other times when there are too many reductions in the population that is called the bottleneck. Drift is probably common in populations that undergo regular cycles of extinction and recolonization. This is extremely important to ecosystems, where plants and pathogens are likely to have a patchy distribution where each patch is a small population.

genetic drift "random drift" or "random genetic drift." The sampling error can occur in at least three ways. Try considering these in the context of pathogen populations in plant pathosystems:

Small recurring population size occurs when there are not many host plants in the area to infect, or when the environment is not optimal for infection.
A genetic bottleneck, or severe reduction in population size, occurs when the plant population is removed (e.g. harvest of the crop), or when the environment changes to prevent infection of the plant or to kill the pathogen directly (e.g. periods of hot, dry weather or a deep freeze).
A founder effect occurs when a small number of individuals, representing only a small fraction of the total genetic variation in a species, starts a new population. A founder event occurs when one or two infected plants slip through a quarantine and introduce a disease into an area where the disease did not previously exist.

Genetic drift also has two significant longer-term evolutionary effect. Genetic drift can facilitate speciation (creating a new species) by allowing the accumulation of non-adaptive mutations that can facilitate population subdivision. Drift also facilitates the movement of a population from a lower fitness plateau to a higher fitness plateau according to the shifting balance theory of Sewall Wright.

Sewall Wright is considered as Darwin's successor. Having a PhD in biology, the idea of genetic drift came, when he published his book called "Evolution and the Genetics of Populations"

Examples of genetic drift are sometimes hard to find, but there are some that are right under our noses.

1. Breeding of dogs
If you look at a chart of dogs, you can see there are probably more than a hundred and fifty types of dogs. All most likely coming from the same dog at a certain time in the past.

2. Breeding of Live Stock
Farmers work with live stock eveyday, tyring to breed the best cattle they can. They have to think about what cow do they want to breed with the bull.

3. Breeding of horses
Specialy race horses. Owners have to look at the mare or stallion to see if they are strong enough to mate with another to pass down the right genes.

Links:
http://evolution.berkeley.edu/evosite/evo101/IIIDGeneticdrift.shtml
http://www.apsnet.org/education/AdvancedPlantPath/Topics/PopGenetics/Pages/geneticdrift.htm
http://www.nndb.com/people/234/000103922/