Genetics

Why do offspring look like their parents? Parents pass half of their DNA to their offspring Heredity (Inheritance) - The passing of traits from one generation to the next

Inherited Traits – characteristics that are passed from parent to offspring –Examples: Eye color, Hair type, Face shape, Blood type

Chromosomes and Genes

Chromosome – A structure found in the nucleus of a cell that contains DNA You have 46 chromosomes in every cell! (23 from mom and 23 from dad)

Gene – A segment of DNA on a chromosome How many genes are on this chromosome? 9 One Gene

Our genes determine our traits Genes always come in pairs One gene from the pair is called an allele.

We talk about genes in 2 different ways: Genotype – the pair of genes (the 2 allele letters) Phenotype – the physical expression of the genes (what it looks like) Rr Genotype Phenotype

Dominant and Recessive Genes

Dominant Trait – will be expressed in the phenotype when at least one UPPERCASE letter is present in the genotype –Dominant Genotypes: RR & Rr

Recessive Trait – will only be expressed in the phenotype if two lowercase letters are present in the genotype –Recessive Genotype: rr

Environmental factors can affect our traits –Nutrients affect: height, weight, health –Temperature affects: fur thickness, color of leaves –Injuries cause: scars –Sun Exposure affects: skin color, hair color