Final answer:
Alternate forms of the same gene are known as alleles. These genetic variations impact an organism's phenotype and contribute to its genotype, determining whether an organism is homozygous or heterozygous for a trait, and leading to a diversity of traits in a population.
Step-by-step explanation:
Alleles are essential in the study of genetics as they are the variations of a gene that arise by mutation and are found at the same place on a chromosome. These genetic variations directly impact the expression of a genetic trait or phenotype. In diploid organisms like humans, two alleles for each gene are inherited—one from each parent. If both alleles are identical, the organism is referred to as homozygous for that trait. Conversely, if the two alleles are different, the organism is called heterozygous for that trait.
Alleles play a significant role in determining an individual's genotype, the combination of alleles that they possess. This genotype contributes to the phenotype—the observable traits of the organism. Due to the importance of alleles in genetics, several key concepts such as dominant and recessive alleles, codominance, and multiple alleles come into play. Highlighting the diversity of genetic make-up, multiple alleles can exist at the population level, leading to a wide range of genetic combinations and phenotypes within a species.