Genetic Variation Label the following diagram



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Genetic Variation

Label the following diagram



Humans have ­­­__ pairs of chromosomes in every cell. They exist in pairs because you get ____ of them from your mother and half from your _______.

Egg cells and sperm cells are called gametes. Each gamete contains half of the parents 46 chromosomes, one of each pair.

A gene is a section of DNA which codes for a specific characteristic e.g. hair colour. Since we have two of each chromosome, we have two copies of each gene, these are called alleles. You get one from each parent.

You can be homozygous; both alleles are the same or heterozygous where each allele is different.

Some genes are dominant and some are recessive. A dominant gene always expressed if present and a recessive gene only shows if there are two copies.

Your phenotype is a description of the characteristics that are shown.

Your genotype is a description of the exact combination of genes you have.

Brown hair (B) is dominant over blonde (b). If my phenotype is brown, I have brown hair, my genotype could be Bb (heterozygous) or BB (homozygous).

Worked example.



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