Origin of Genetics

Gregor Mendel: Father of Genetics

I should cross a 2 different types of Pea Plants and see what the offspring looks like.

Why use Peas Plants:* Seeds available* Grow quickly* Large # of offspring* Lots of different types of traits

Vocabulary Terms:Genetics - scientific study of heredityP Generation - Parental generationsF1 Generation - First Generation from P generationF2 Generation - Second Generation from P generationDominant Genes - genes that mask other genes (Capitalized letter)Recessive Gene - hidden unless there are 2 (lowercase letter)Homozygous - Two of the same traitsHeterzygous - Two different traitsAllele - either member of a pair of genesGenotype - Pair of alleles (genes)Phenotype - Trait expressed (what you see)Monohybrid Cross - Cross involving only 1 traitDihybrid - corss involving 2 traitsIncomplete Dominance - occurs when both alleles for a trait are expressedCo-Dominance - both alleles for a gene are expressed (neither is dominant or recessive)

Dominant and Recessive Traits

Origin of Genetics

Discovery of Gene Dominance

Step 1: Cross 2 Pure-Breed Plants with contrasting traits.Found that all offspring had purple flowersStep 2: Take offspring of the plants in step one and cross them.Found that 1 out of 4 plants had white flowers. (3:1 Ratio)

Mendel's Conclusions:Genes govern expression of traitsP = Purplep = White* F1 Generation genes were Pp

Dominate Gene masks other gene* Indicated by Capital Letters Example: P = Purple FlowerRecessive Gene is hidden* Indicated by Lowercase LettersExample: p = white flower

Law of Segregation

Law of Independent Assortment

Law of Segregation: The number of each pair of genes separate or segregate when gametes are formed.

Law of Independent Assortment: Two or more pairs of genes segregate independently of one another during gamete formation. Occurs in Meiosis