Explain the evolutionary mechanisms that can change the composition of the gene pool - Essay Example

Mechanisms that introduce genetic variation Evolution is a process by which changes occur in the gene pool of a particular population over a given period. Genetic variations form the basis of evolution as they introduce subtle changes within an individual which differentiates every living being from each other. Mechanisms that introduce such variations exist at the cellular and molecular levels and they can either increase or decrease genetic variations. Three such mechanisms that increase genetic variations include mutation and built-in variation within an organism, genetic recombination and gene flow within a population.

In addition, certain evolutionary processes such as natural selection and genetic drift cause a decrease in these genetic variations (Colby; Lerner). Mutation is a phenomenon by which chemical changes occur within the DNA which in turn alters the sequence of the gene resulting in a mutant gene. The extent to which the DNA is altered depends on the type of mutation which could be a point mutation in which on letter of the genetic code is changed, insertion or deletion of a stretch of DNA within a gene or inversion, translocation or duplication of a segment of the DNA.

Such mutations can produce truncated proteins, abnormal proteins or a silent mutation that does not introduce any change in the resulting protein. Hence a mutation can have both a deleterious as well as a beneficial effect on the organism (Colby; Lerner). In addition to mutation, gene expression within an organism also depends on the built-in natural variation that occurs within a gene pool. Not all genes within an organism are expressed as only those which are activated produce their respective proteins and are hence expressed in the phenotype.

Such selective expression of genes is also responsible for the variations observed between each individual (Veith). Genetic recombination that occurs during the union of the male and female gametes is also an important source of genetic variation. The haploid male and female gametes unite through meiosis in which the DNA of the two combining homologous chromosomes are broken at various points and rejoined by the process of independent assortment and crossing over to restore the diploid number of the chromosomes.

This genetic rearrangement that occurs by chance during meiosis results in a new genotype and the variations are observed in the resulting phenotype (Colby; Lerner; Veith). The third mechanism that can cause genetic variation is through gene flow which occurs when organism migrates from one population to another and by mating within the new population new genes are introduced into that population. Infrequent gene flow between distantly related species can also result in subsequent spread of new genes within the species (Colby; Lerner).

In the process of natural selection, variant genes introduced within a population and which are unfit for survival are removed thus leaving the more adaptive genes to survive and reproduce within the population. Individuals who possess a genotype that would increase their fitness levels are invariably selected over others whose genotypes would prevent them from adapting to their environment, hence causing them to perish. Under this evolutionary process individuals are expected to adapt to their changing environmental conditions such as in the case of penguins which have evolved from flying ancestors to flightless animals which use their wings for swimming.

Another factor that could introduce a change in the composition of the gene pool is genetic drift. By this process the alleles carried from one generation to another varies in frequency owing to chance which could result in changes within the gene pool. This process is a random event and hence is independent of the size of the population (Colby). In addition genetic drift can also be affected by certain environmental factors such as geographical barriers, catastrophic events such as natural disasters, wars and other socio-political factors as these events profoundly affect the reproductive ability of the population in which they occur (Lerner).

Thus the changes that occur within the gene pool could be a result of a number of factors as mentioned above which could either increase or decrease alleles within the gene pool. Reference 1. Colby, Chris. “Introduction to Evolutionary Biology.” Talkorigins.org. The TalkOrigins Archive, 1996. Web. 22 Apr. 2011. < http://www.talkorigins.org/faqs/faq-intro-to-biology.html > 2. Lerner, K. Lee. “Evolutionary Mechanisms.” Science.jrank.org, n.d. Web. 22 Apr. 2011. http://science.jrank.org/pages/2613/Evolutionary-Mechanisms.html 3. Veith, J. Walter. “Mechanisms for Variation.

” Amazing discoveries.org. Amazing Discoveries, n.d. Web. 22 Apr. 2011. http://amazingdiscoveries.org/C-deception-gene_variation_classification.html