What are alleles?

Alleles are defined as alternate forms of a gene. In genetics, each gene resides in a specific location on a chromosome, and variations in the DNA sequence at that location give rise to alleles. For example, a gene that determines flower color in pea plants may have an allele for purple flowers and another allele for white flowers. Each of these variations can affect the trait expressed by the organism.

Understanding that alleles represent different forms of a gene is fundamental in the study of heredity and how traits are passed from parents to offspring. The presence of multiple alleles for a single gene can lead to a range of possible traits, contributing to genetic diversity within a population. This concept is crucial for comprehending dominant and recessive inheritance patterns and the overall principles of Mendelian genetics.

The other options do not accurately capture the definition of alleles. The idea of identical copies of a gene refers to homozygous conditions rather than allelic variation. The notion of different forms of a disease and variants due to environmental factors does not pertain to the genetic distinction of alleles but rather to the broader discussions of disease genetics and phenotypic variation influenced by external factors.