Chapter 9:1 Mendel’s Legacy

Gregor Johann Mendel Born 1822: Austria Son of a peasant farmer At 21, entered monastery in Brunn, Austria Ordained into priesthood Studied math and science at University of Vienna Returned to monastery taught school and kept a garden

Experiments in Heredity Garden Pea (Pisum sativum) Today Molecular Genetics:

Garden Peas: Traits have 2 different forms

Mating is easily controlled Male and Female reproductive parts on same flower 1.Self-Fertilization 2.Cross pollinate

Get Results Quickly Plants are small, grow easily Produce many offspring quickly

Mendel’s Experiments: One contrasting trait 1.Garden pea was self-pollinated for several generations a.Ensures True-Breeding: that all the offspring would display only one form of a trait b.Parental Generation (P Generation) Example: All Purple Flowers All White Flowers

2. Crossed 2 P Generation plants that had contrasting traits Example: Purple Flower x White Flower -offspring gave 1 st generation plants (F 1 Generation)

3.F1 generation self-pollinated - gave 2 nd generation (F 2 generation)

Results 1.F1 plants showed only 1 form of trait (Purple) 2.Contrasting trait (white) disappeared 3.F2 plants-contrasting trait (white) appeared in some Ratio 3:1

Conclusion For each individual trait, an individual has two copies of the gene-one from each parent There are alternative versions of genes (called alleles) When two alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’s appearance Dominant: Trait that is expressed Recessive: Trait that is expressed only when both recessive alleles re present

Conclusion cont. Law of Segregation: pair of factors is segregated, separated, during the formation of gametes Law of Independent Assortment: factors separate independently of one another during formation of gametes