A study from South Africa finds that while protective HLA-B alleles once aided survival and reduced HIV transmission before Antiretroviral therapy, widespread ART use has significantly slowed this natural selection-driven genetic shift.
About Alleles:
An allele is a variant form of a gene.
Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome.
Humans are called diploid organisms because they have two alleles at each genetic locus, with one allele inherited from each parent.
Each pair of alleles represents the genotype of a specific gene.
Genotypes are described as homozygous if there are two identical alleles at a particular locus and as heterozygous if the two alleles differ.
Alleles contribute to the organism's phenotype, which is the outward appearance of the organism.
Some alleles are dominant or recessive. When an organism is heterozygous at a specific locus and carries one dominant and one recessive allele, the organism will express the dominant phenotype.
This genetic diversity allows offspring to inherit traits from both parents while exhibiting unique characteristics.
For example, in hair color, dark hair is typically dominant over light hair; a child may inherit light hair only if both parents pass on the recessive allele.
All genetic traits are the result of the interactions of alleles.
Mutation, crossing over, and environmental conditions selectively change the frequency of phenotypes (and thus their alleles) within a population.
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