AQA A Level Biology

Revision Notes

4.1.5 Genetic Loci

Genetic Loci

Genes, loci and alleles

  • The DNA contained within chromosomes is essential for cell survival
  • Every chromosome consists of a long DNA molecule that codes for several different proteins
  • 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

Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

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