The study of heredity

Genetics

1860’s Austrian MonkWorked with pea plantsUsed 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 letters2.Set up cross3.Create Punnett square4.Determine genotypes5.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.