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Introduction to Genetics:

Read pp 117-122 in your books!

Remember that Meiosis is sexual reproduction, wherein special sex cells within the ovaries or testes first double their chromosome number (from 46 to 92), then in a series of two divisions, create eggs or sperm with one-half the normal chromosome number (23).

Genetics- Study of how traits are inherited or passed between generations.

Chromosomes- Part of cell nucleus that controls what the cell does, & thus controls all your traits. Humans = 46 chromosomes.

Genes- Small sections of chromosome that are responsible for making 1 trait. Each person has at least 1 pair of genes (1 from mom, 1 from dad) for each trait.

The gene pairs are called alleles.

Dominant Gene- The stronger gene of a gene pair. Shown by a capital letter (A, T, E, R......)

Recessive Gene- The weaker gene of a gene pair. Shown by a lower case letter (a, t, w, r.....). If a person has both a dominant & recessive gene, the recessive one isn't seen. For a person to see a recessive trait, the person must have 2 recessive genes in the gene pair (Ex....aa, tt, ww, rr...).

Homozygous- Both alleles (genes) of gene pair are identical. AA, tt, yy, BB, nn......

Heterozygous- Both alleles (genes) of gene pair are different. Aa, Tt, Yy, Bb, Nn.......The dominant (big letter) allele wins out & is shown.

Genotype- The 2 "gene" or allele letters a person has for a trait. Examples: AA, Tt, rr, Ww, ii, QQ.

Phenotype- What the trait looks like (blue eyes, brown eyes, black hair, blonde hair, light skin, dark skin, etc....)

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