Alleles (Edexcel IGCSE Biology)
Revision Note
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
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