3.17 understand the meaning of the terms: dominant, recessive, homozygous, heterozygous, phenotype, genotype and codominance

Dominant - If an allele is dominant, the characteristic controlled by a dominant allele develops if the allele is present on one or both chromosomes in a pair. A dominant allele is always shown with capital letters. For example, 'BB'

Recessive - if the allele is recessive the characteristic controlled by a recessive allele develops only if the allele is present on both chromosomes in a pair. If there is only one recessive allele present, the characteristics of the dominant allele will show. A recessive allele is portrayed with lowercase letters. For example, 'ee'.

NOTE:  If you have two alleles, the version of the characteristic that appears will be dominant. For example, if you inherit one allele for brown eyes (BB) which is dominant and one allele for blue eyes (ee) which is recessive, the dominant characteristic will show, so you will have brown eyes. The only way you could have blue eyes is if you inherited two alleles for blue eyes. as this allele is recessive.

Homozygous - If you are homozygous, you have inherited two of the same alleles (e.g. BB or ee). All this means is that you have inherited, for example, two alleles for blue eyes or two alleles for brown eyes.

Heterozygous - If you are heterozygous, you have inherited two different alleles for that particular gene (e.g. Bb). All this means is you have most likely inherited one recessive and one dominant, in which case the characteristics of the dominant allele will show.

Phenotype - The phenotype is the characteristic that the alleles produce. For example, brown eyes, blonde hair, brown hair, blue eyes and so on.

Genotype - The genotype is the allele configuration you have inherited. For example, 'Bb', 'BB', 'ee' and so non.

Codominance - If you happen to inherit two dominant alleles, this is called codominance. This is where neither allele is recessive so you show characteristics from both alleles, as one is not dominant over the other. For example, blood group A is dominant and so is blood group B, so if you inherit an allele for A and an allele for B, you will end up with blood group AB.