Question

6. a. Explain how individuals of a species are distributed when the species exhibits Population Structure. Include the following terms in your answer:

           Deme (=Subpopulation), Total Population.

      b. In population genetics what is meant by migration between subpopulations of a species, and why will migration tend to keep subpopulations similar genetically.

      c. Suppose you have 100 demes of a species, each with N=100, and each with allele frequencies f(A) = 0.5 and f(a) = 0.5. Draw two graphs representing how genetic drift will affect allele frequencies in the 100 populations; i. when no migration is occurring among demes, ii. when a moderate amount of migration is occurring among the demes.

Answer 1

Ans.(a..).Population structure is one of the most studied & least understood of population geneticsBy population structure, population geneticist means instead of single,simple population,it subdivided in some way.The 'overall population of populations' is called metapopulation,and individual component of population is called subpopulation,but also local population or deme.if populagions are subdivided,they can evolve apart,somewhat independently. Population structure allows to population diversify.The term "population structure "or("population subdivision) usually refers to pattern in neutral genetic variation that result from the past or present departure from panmixia of population.In effectively continuous populations, different areas can have different gene frequencies,because whole metapopulation is not panamictic..Understanding the past population structure is of interest to evolutionary biologists because it can reveal when migration regims changed in natural populations,thereby pointing to potential environmental factors such as climate changes as driving evolutionary forcesCharacterising the structure of extent populations is also a key to conservation genetics as translocation and reintroduction decision .it must preserve evolutionary stable units.Finally ,population structure has important biomedical consquences either when a number of subpopulation groups is locally adapted to particular environmental conditions( and maladapted when exposef to new environments)or represents confounding factor in study of the statistical association between the genetic variants & phenotypic traits.Ans.(b).Gene flow is the exchange of genes between popultations or species,breaking down the structure.The accuracy of gene flow or migration estimates is unknow in most natural populations bevause direct estimateif dispersal are not possible.These estimates can be highly imprecise or biased because population genetic structure reflects mor than a simple balance between gene drift and gene flow.Migration or gene flow is the transfer of genetic variation from one population to another in population genetics.If a rate of gene flow is high enough,then two populations are considered to have equivalent genetic diversty& therfore effectively a single population. It is an important mechanism for transferring genetic diversity among population.In most of distributed evolutionary algorithms(DEAs),migration interval is used to decide frequent of migrationThe regional model (migrational model)divide population s into multiple individual subpopupulations.These subpopulation evolvve independently of each other for a certain number of generations(isolated time).The most general migration strategy is that of of unrestricted migration(complete net topology).Individuals may migrate from any subpopulation to another population.Gene flow is transfer of alleles from one populations to another populations through immigration of individuals..The individual migrants are then uniformaly at random determined from potential pool.Genetic drift is a chabge in allele frequencies caused by random sampling.Ronald Fisher held the veiw that genetic drift plays at most a minor role in evolution,& this remained the dominant veiw for several decades.