Genetics The scientific study of heredity Every living thing has a set of characteristics inherited from its parent or parents

Chromosomes Located in the nucleus Structure Tightly coiled (compact) Contains genetic information

Genes and Dominance Trait – specific characteristic Examples: eye color, blood type Hybrid – cross between parents with different traits Genes – small section on a chromosome that determines a specific trait Alleles – different forms of a gene Each gene is composed of 2 alleles (dominant or recessive)

Genes and Dominance (cont.) Dominant gene – prevents other genes from showing their traits Shown by a capital letter (G) Recessive gene – does not show its trait when dominant genes are present Shown by a lower-case letter (g)

Gregor Mendel Father of genetics Crossed true-breeding pea plants and studied the results He discovered two things: Law of segregation – each reproducing individual has 2 alleles for each trait Law of Independent Assortment – the acquisition of 1 trait does not influence the acquisition of another.

Principle of Dominance States that some alleles are dominant and others are recessive Homozygous – the 2 alleles are identical Both are either dominant (GG) or recessive (gg) Heterozygous – the 2 alleles are different One allele is dominant and one is recessive (Gg) The dominant trait will always hide the recessive trait

Single Crosses A single cross can be used to predict the trait of an offspring between two individuals This is done using the Punnet Square Method: Traits from each parent are shown along the sides B B Example: This is a cross between an individual homozygous dominant for brown eyes (BB) and another individual homozygous recessive for blue eyes (bb) All offspring are heterozygous and have brown eyes Bb b

Practice Cross an individual heterozygous dominant for brown hair (Bb) with an individual recessive for blond hair (bb)