Genetics and Heredity Our Hero Gregor Mendel

Mendle’s Pea Experiment Height-Tall vs Short Seed Shape-Round vs Wrinkled Seed Color-Yellow vs green Flower Color- Purple vs White Flower Position- Axial vs Terminal Pod shape- Inflated vs Constricted Pod Color- Green vs yellow

Anatomy of a Flower

Making A Punnett Square

Gametes TT X tt Male Female

Completed Square TT Male X tt Female T T t t

Terminology Homozygous-two of the same alleles for a given trait Dominant Recessive Heterozygous-each cell of an organism contains two different alleles for a given trait Example:

Tt X Tt

More Terminology Genotypic Ratio- the combination of alleles for a given trait (gene combination) Phenotypic Ratio- a ratio of what the offspring look like

Test of Segregation Test cross Rr X rr RR X rr

Mendle’s Conclusions Principle of Dominance- one form of a hereditary trait (dominant), dominates or prevents the expression of the recessive trait. Principle of Segregation- during gamete formation the pair of genes responsible for each trait separates so that each gamete receives only one gene for each trait.

IncompleteIncomplete Dominance

DihybridDihybrid Cross

THE PRINCIPLE OF INDEPENDENT ASSORTMENT GENES FOR DIFFERENT TRAITS SEGREGATE INDEPENDENTLY DURING GAMETE FORMATION

Multiple Alleles-Codominance Blood type A Blood type B Blood type AB Blood type O IAIAIAIA I A i O IBIBIBIB IBiOIBiO IAIBIAIB iOiOiOiO G e n o t y p e s

Mendel’s Work Revisited In the early 1900’s Walter Sutton observed meiosis in grasshoppers. He concluded that chromosomes do indeed behave like Mendel had thought. It also started the idea that genes are on the chromosomes.

Thomas Hunt Morgan His work was on fruit flies Experimented with the sex chromosomes X and Y chromosomes differ between the sexes so they are called sex chromosomes The other chromosomes are called autosomes

Sex Determination MaleFemale

Sex-Linked Inheritance XRXRXRXR XrYXrY Red Eyed FemaleWhite Eyed Male

Can We Get A White Eyed Female? XRXrXRXr XrYXrY Red Eyed FemaleWhite Eyed Male