Genetics = Study of Heredity

Introduction A. Heredity = passing of characteristics from parent to offspring a.Trait = characteristics that are inherited b. Gregor Mendel = “Father of Genetics” ( ) I. Monk, scientist, gardener, teacher II. Studied thousand of pea plants; with distinct traits III. Simplify problems; meticulous data collection and record keeping; think quantitatively

B. Mendel’s Discoveries a. Rule of Unit Factor I. Gene = segment of DNA on a chromosome that controls a particular trait; exists in alternate forms II. Allele = contrasting form of a gene

b. Rule of Dominance I. Dominance = trait masks or “dominates” another trait; represented by Capital letter II. Recessive – trait that is masked by dominant trait; seems to disappears; represents by small letter Being able to roll your tongue is a dominant trait.

II. Crosses A. Terminology a. Phenotype = external appearance; how an organism looks b. Genotype = gene combination of an organism; it’s genetic makeup (Bb) c. Homozygous = 2 alleles for the trait are the same: TT or tt d. Heterozygous = 2 alleles in the pair are different; Tt

B. Monohybrid Crosses = cross between individuals that involve one pair of contrasting traits. a. Punnett Square = diagram to aid in visualizing the results of a cross.

Monohybrid Crosses (Examples) Ex 1: Pure Tall x Pure Short T=Tall t=shortT t t Tt TtTt TT Tttt 100% Tall 25% pure tall 50% hybrid tall 25% pure short (Homozygous x Homozygous) (Heterozygous x Heterozygous)