Genetics- the study of heredity. Heredity is the passing of characteristics from parent to offspring.

Gregor Mendel-Father of Genetics Gregor Mendel- 1840’-1860’s did research on heredity. An Austrian Monk who became the Father of Genetics. Used Pea plants to do test- crosses.

Genetic Crosses Parent generation (P1) the first two organisms that are crossed F 1 generation - offspring from first generation F2 generation-offspring from crossing the F 1 generation. Common in plants and animals

Mendel’s 4 Principles 1.1. The principle of dominance states that some alleles are dominant and some are recessive. 2. The principle of probability can be used to predict offspring outcome.

3. The principle of independent assortment states that alleles for different genes usually separate independently of each other. 4. The principle of inheritance of biological characteristics -genes are passed from parent to offspring.

Dihybrid Crosses When two traits that separate independently of each other are put into a cross you get 16 Offspring.When both individuals are heterozygous you get a 9:3:3:1- phenotypic ratio. (what they look like)

Section 11-3 Figure Independent Assortment in Peas Go to Section:

Beyond Simple Dominant and Recessive Alleles Some alleles are neither dominant or recessive, and multiple alleles or multiple genes control many traits Incomplete Dominance- The phenotype of the offspring is intermediate (blend) of the parents. Example :red flowers x white flowers make pink.

Example Incomplete Dominance

Co-Dominance Both alleles are expressed equally giving striping spots or checkered appearance. Example: some chickens have equal number of white and black feathers giving a checkered appearance. In cattle red cattle and white cattle make roan cattle (some red patches some white)

Multiple Alleles- In the population of organisms there are more than two alleles for certain traits. An individual can only have 2 alleles for each trait but more can exist in the population. Example: Human blood type A, AB, O, B

Polygenic Traits Trait produced by the interaction of several genes. This causes a wide variation in outcomes. Example: Human skin color –controlled by 4 different genes

Sex-Linked The trait is on the Chromosome that determines the sex of the offspring. Females=XX Males=XY Because males only receive one X from their mother if the trait is on the X it will show up even if it is recessive. Y chromosome is very small and does not carry many traits. Examples: Color-blindness, hemophilia