BRAINCAKEAlleles
An allele is a different version of the same gene. Alleles of a gene are found at the same locus on homologous chromosomes and differ slightly in their base sequence, so they may code for slightly different polypeptides. For example, a pea plant gene for height has an allele for tall and an allele for short. New alleles arise by mutation.
A diploid organism has two alleles for each gene, one on each chromosome of the homologous pair.
• Homozygous: both alleles are the same (TT or tt).
• Heterozygous: the two alleles are different (Tt).
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