Genetic Loci (AQA A Level Biology): Revision Note

Genetic loci

• DNA contained within chromosomes is essential for cell survival

• A length of DNA that codes for a single polypeptide or protein is called a gene

• The position of a gene on a chromosome is its locus (plural: loci)

• Each gene can exist in two or more different forms called alleles

• Different alleles of a gene have slightly different nucleotide sequences, but they still occupy the same position (locus) on the chromosome