What are alleles?

Alleles are defined as alternate forms of a gene that occupy the same position on homologous chromosomes and can result in different traits. For example, a gene that determines flower color in a plant may have one allele for red pigmentation and another for white. These variations arise due to slight differences in the DNA sequences of the gene. When an individual carries two different alleles for a particular trait, this genetic diversity is essential for the variation in traits seen within a population.

The other options imply different concepts: while different sequences of DNA could theoretically describe alleles, they are more accurately categorized as variations of the same gene rather than distinct entities. Referring to males and females of a species does not relate to the genetic concept of alleles, as it pertains to biological sex rather than genetic variation. Lastly, describing traits expressed in DNA fails to capture the essence of alleles, which specifically denote the alternative forms derived from a particular gene rather than traits themselves.