The study of heredity Genetics

1860’s Austrian Monk Worked with pea plants Used his math background to make new hypotheses about inheritance. Gregor Mendel

Mendel’s Experiments

Example of Mendel’s work

2 or more “factors” for each trait Dominant-more powerful, always shows (R) Recessive-weaker, sometimes shows (r) Mendel hypothesized that each trait is controlled by a “factor”

Mendel knew that 2 parents contribute to inheritance. Therefore, each organism must have 2 factors for each trait. These factors later became known as genes.

Purebred (homozygous) both genes the same RR, rr Hybrid (heterozygous) genes are different Rr

1. Law of Segregation – genes separate when gametes form Mendel’s 3 Laws

2. Law of Dominance – when 2 different alleles in a gene pair are present only one gene is expressed

3. Law of Independent Assortment – gene pairs segregate into gametes randomly and independent of each other.

Genotype – the actual genetic makeup of the organism (letters) Phenotype – the form of the trait expressed (word)

Used to predict the outcome of a genetic cross. Punnett Square

1.Assign letters 2.Set up cross 3.Create Punnett square 4.Determine genotypes 5.Determine phenotypes Dihybrid Cross: 2 factors

Golden fur is dominant over silver fur. Long fur is dominant over short fur. 1. Cross a homozygous golden long furred dog with a heterozygous golden furred dog with short hair.

Golden fur is dominant over silver fur. Long fur is dominant over short fur. 2. Cross a homozygous silver long furred dog with a heterozygous golden long furred dog.