In basic genetics, what is an allele?

• A. An alternative form of a gene found at the same locus on homologous chromosomes
• B. The physical location of a gene on a chromosome (a locus)
• C. A pair of identical sister chromatids joined at a centromere
• D. A segment of DNA that encodes an entire chromosome

Answer: (A)

Verified step by step guidance

1. Understand that genes are segments of DNA that code for specific traits.
2. Recognize that each gene can have different versions, which are called alleles.
3. Know that alleles occupy the same position, or locus, on homologous chromosomes.
4. Identify that an allele represents an alternative form of a gene, which can result in variations in the trait it controls.
5. Distinguish alleles from other genetic terms such as locus (the gene's position), sister chromatids (identical copies of a chromosome), and entire chromosomes (large DNA molecules).