What are alleles?

• A. Structural proteins
• B. Different versions of a gene
• C. RNA molecules
• D. Cell receptors

Answer: (B)

Alleles are defined as different versions of a gene. In genetics, a gene is a specific sequence of DNA that encodes for a protein or functional RNA molecule. Each gene can have multiple variations, known as alleles, that arise due to changes in the DNA sequence. These variations can lead to differences in traits among individuals—such as eye color, plant height, or disease susceptibility—because alleles may affect the function or expression of the corresponding gene.

For example, the gene responsible for flower color in pea plants has alleles that can produce purple or white flowers, thereby illustrating how alleles contribute to phenotypic diversity. This concept is central to understanding inheritance patterns and genetic variation in populations.

The other choices do not accurately describe what alleles are. Structural proteins refer to proteins that provide support in cells and tissues; RNA molecules relate to the roles of ribonucleic acid in coding, decoding, regulation, and expression of genes; and cell receptors are protein molecules that receive and transmit signals across the cell membrane. None of these choices captures the essence of alleles as variations of a specific gene.