# GENE POOLS & ALLELE FREQUENCY

#### branchEVOLUTION

Coming from EVOLUTION
==Gene Pool== A gene pool is the sum total of the genes (and their alleles) present in a population [image:http://i.imgur.com/iJdYAt0.png?1] The living things we see around us and their heritable traits are simply the outward expression of their genes. You can think of an organisms adaptations as the medium through which its genes interact with the environment. While every organism eventually dies, its genes can survive through the production of offspring. Evolution is essentially a study of the mechanisms that determine the success and subsequent increase of certain genes and the demise of others. ==Population== A population comprises the total number of one species in a particular area. Because all members of a population are the same species they have the potential to interact and breed with each other. Individuals that are isolated from one another are members of different populations. ==Allele Frequency== The allele frequency is simply proportions of each allele (different versions of a gene) within a population. The allele frequency may give some indication as to which version of the gene (allele) provides the greatest adaptive advantage. The allele frequency can be calculated by counting the number of each allele and converting them to percentages. For instance for the population depicted above the frequency of the ''A'' (dominant) allele can be calculated as follows: [image:http://i.imgur.com/STTYIJQ.png] The allele frequency of the ''A'' (dominant) allele is approximately 53% [image:http://i.imgur.com/xEzTZ8O.png?2]] Many textbook examples only involve two different versions of a gene -a dominant and a recessive version. In reality there are often many different versions of a gene (alleles) within a population. Often there is an order of dominance. For instance, in this example the '''''A''''' allele is dominant over both the '''''a''''' and '''''a^-^''''' alleles, but is recessive to the '''''A^+^''''' allele. ==Genetic Equilibrium & Factors that affect Allele Frequency== If the allele frequency is no longer changing in a population a genetic equilibrium has been reached. However, several factors can easily disrupt this genetic equilibrium and later the allele frequency. The factors include: • ''Genetic Drift'' • ''Natural Selection'' • ''Artificial Selection'' • ''Sexual Selection'' • ''Gene Flow'' (Immigration & Emigration) • ''Mutations'' • ''Founder Effect'' • ''Population Bottlenecks''
Credit: Ben Himme