Gregor Mendel Chapter 10

Gregor Mendel Gregor Mendel: “Father of Genetics” Austrian monk Conducted several experiments on pea plants His work lead to the foundation of modern genetics

Mendel’s Experiments Cross-Pollination: breeding of 2 different plants (pea plants) P generation: “parent”; original strains purple x white F1 generation: “filial”; offspring of P gen. all appear purple F2 generation: offspring of self-pollinating F1 gen. 3/4 are purple, 1/4 white

Why Peas??? 1) Peas have distinct characteristics which could easily be studied Height, flower color, pea shape, etc. 2) Mendel could control pea reproduction He could cross-pollinate them OR make them self-pollinate 3) Mendel chose true-breeding plants (“homozygous”) Caused the recessive trait (white flowers) to be “hidden” in F1 gen., then reappear in F2 gen.

Mendel’s Principles Principle of Dominance Some alleles are dominant others are recessive Law of Independent Assortment Each adult has 2 alleles/gene; one from each parent Alleles for different genes separate independently

Exceptions to Mendel’s Principles 1) Incomplete Dominance: phenotype is in between those of parents i.e.: hazel eyes, wavy hair 2) Codominance: both alleles are expressed in phenotype i.e.: 2 diff. color eyes, spots in animal fur

Exceptions to Mendel (con’t) 3) Multiple Alleles: gene has more than 2 alleles Results in more possible combinations Individuals still only inherit 2 alleles i.e.: blood type = 3 alleles 4) Polygenic Traits: traits controlled by 2 or more genes Leads to wide range of phenotypes i.e.: skin color = 4 + genes