Genetics Chapter 9.1

Genetics Genetics - the study of genes and heredity

Heredity Heredity – passing of traits from parents to offspring through genes

Traits Traits - characteristics that are inherited through genes

Gregor Mendel A monk in the 1800s First to identify heredity Father of Genetics

Garden Peas Studied the traits in garden peas –Tall/short –Round/wrinkled –Green/yellow pods –Purple/white flowers

Alleles Each trait or characteristic has 2 copies of DNA that code for that trait Each copy of the trait is called an allele Different form of a gene

The Rule of Dominance Alleles can be either dominant or recessive (strong or weak) –Dominant (A) alleles are observable –Recessive (a) alleles are not usually observable, when the dominant allele is present

Dominant The allele that is expressed – you can see it Represented by capital letters C curly hair B brown hair

Recessive The allele that is not expressed when covered up by the dominant allele –It is there you just cannot see it Use the lower case for the recessive allele c for straight hair b blonde hair

Genotype The copies of alleles or genes that an organism has BB, Bb, bb/ TT, Tt, tt

Phenotype The way an organism physically looks –Brown hair, tall

Homozygous (homo = same) Pure When an organism has 2 copies of the same allele BB – homozygous dominant bb – homozygous recessive

Heterozygous (hetero = different) Hybrid When an organism has 2 different alleles for a gene Bb, Gg, etc.

The Law of Segregation Alleles for a gene separate when forming a sperm and egg

Law of Independent Assortment Alleles for different genes are distributed to sperm and egg independently Could be –tall and fat –short and thin –tall and thin –short and fat This is why all siblings do not look exactly alike

So…