Alleles (Edexcel IGCSE Science (Double Award))

Alleles

• A gene is a short length of DNA found on a chromosome that codes for a particular characteristic (expressed by the formation of different proteins)

• Genes exist in alternative forms called alleles

• Alleles are variations of the same gene

  • As we have two copies of each chromosome (one from each parent), we have two copies of each gene and therefore two alleles for each gene

  • One of the alleles is inherited from the mother and the other from the father

  • This means that the alleles do not code for the same thing

  • For example, an individual has two copies of the gene for eye colour but one allele could code for brown eyes and one allele could code for blue eyes

• Having alleles give rise to differences in inherited characteristics and variation within species