DOMINANCE AND RECESSIVENESS

The pattern of genes in an individual is known as its genotype. The appearance of the individual is called the phenotype.

As each cells in the body contains a pair of each chromosome, this means that they also carry two copies of each gene.

These genes may be the same (homozygous) or different (heterozygous). Different forms of the gene are known as alleles

If two genes are present, one may dominate over the other. This is known as the dominant gene, while the other is the recessive gene

eg.   in humans, dark eye colour is dominant over light eye colour
       B - dark eye colour allele
       b - light eye colour allele

● dark eyes -> BB (homozygous) or Bb (heterozygous)

light eyes -> bb (homozygous)

In some cases, one allele does not dominate completely over the other. This is called incomplete dominance

eg. colour in snapdragons
R - red allele W - white allele

● red -> RR (homozygous)

white -> WW (homozygous)

pink -> RW (heterozygous)

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