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Genetic Loci (AQA AS Biology): Revision Note

Lára Marie McIvor

Written by: Lára Marie McIvor

Reviewed by: Lucy Kirkham

Updated on

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

Chromosomes showing gene and loci, downloadable AS & A Level Biology revision notes

Five different genes found at five different loci

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    Author
    Reviewer
    Lára Marie McIvor

    Author: Lára Marie McIvor

    Expertise: Biology Lead

    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.

    Lucy Kirkham

    Author: Lucy Kirkham

    Expertise: Head of STEM

    Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.