An allele is a gene that can vary from one person in a sequence to another person’s gene. When the chain of a gene differs noticeably, the various kinds of genes are referred to as alleles. Therefore, allele frequency is the proportion of a population having one particular type of gene. In population genetics, allele frequencies tend to show genetic diversity of a species population or homogeneously the richness of its gene pool. This measure is usually expressed as a percentage.
Allele frequency is also the relative proportion of all alleles of a gene that are of a chosen type in relation to; different alleles of the gene exist, one of the allele exists in a copies and particular locus on a chromosome and the gene occupy that locus. When calculating allele frequency, it is wise to consider the ploidy of the species for autosomal genes. Ploidy is the number of sets of chromosomes in the nucleus of a living organism cell.
Each organism has a distinctive genome, a chain of genes specific to the organism. Individual gene in a given genome holds the data essential for the body fluid to produce suitable cell products. Specific genes in individuals have specific or fixed locations on the genome. Many times, when geneticists look at the human genome, they are able to locate genes that have specific purposes. While the sequence of a gene commands what a product the cells makes from it, and the sequence does not have to be thorough. Thus, why, different people can have a gene at the same place that conducts different things for each person.
The gene for a sickle cell anemia has two important alleles. One of the allele is the normal allele that aids create healthy red blood cells while the other is an allele that makes the red blood cells with an unusual sickle shape. Each person has two copies of a gene, one of the gene is contributed by the father and one by the mother. When a person has only one sickle cell gene, he or she is more resistant to malarial disease. When an individual has two sickle cell genes, he or she is likely to have single cell anemia.
In relation to sickle cell gene, the allele frequency of abnormal gene takes into consideration the number of people in a particular population that has at least one copy of the gene. There are numerous factors that lead to changes in allele frequencies. These include;
- Evolution- This is a process by which new species of organism develop from any early forms. This process is slow, but it changes in the frequency of the alleles in a population.
- Natural selection- Populations produce more offspring than environmental resources can maintain, hence there is competition for survival. Those individuals with best features or adaptations survive and reproduce and pass their successful genes on to their offspring increasing the gene pool.
- Mutation- If mutation occurs in the reproducing cells and during DNA replication for meiosis and the gamete is fertilized then mutation will occur in the pool. However, it is acted upon by natural selection.
- Other factors affecting allele frequencies are migration [both immigration and emigration] and genetic drift [founder effect and bounder effect].
Allele frequency is useful information both for those pursuing genetics or biology. It offers exceptional information for genetic research and for public health interventions such as genetic testing. The Hardy-Weinberg law can also be used to describe the balance of diploids genes in the calculation of allele frequencies.
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