1. Gregor Mendel
Chapter 10

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

3. 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

4. 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.

5. 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

6. 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

7. 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