1. Genetics in History

2. Gregor Johann Mendel
Scientist and Friar; conducted experiments on pea plants from 1856 – 1863
Established the rules of heredity, now known as the laws of Mendelian inheritance
Tested 7 characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color

4. Why did Mendel pick Garden Peas?
Garden peas reproduce sexually
Garden peas can self-pollinate
He could control traits while still allowing for random selection
Mendel was a good scientist
He recorded accurate data
He only tested one trait at a time

5. The first trait Mendel tested was height, and it resulted in hybrids.
Hybrid: offspring that has different forms of the trait. (Tt) than its parents (TT x tt)

6. First Generation Second Generation
He cross-pollinated tall pea plants with short pea plants. Mendel found that
All the pea plants grew to be tall
The short trait had disappeared
He allowed first generation to self-pollinate.
Planted the seeds from the self-pollination.
Grew 1000 plants

7. Mendel discovered that:
¾ were as tall as the parent plants
¼ were short like the parent generation.
They occurred in a ratio of 3:1
The short trait reappeared out of nowhere.
Each trait tested had the same 3:1 ratio!

8. P1 Generation F1 Generation F2 Generation
The original parent or the true breeding plant.
F1 Generation
The offspring of the parent (P1)
F2 Generation
The offspring of the (F1) generation.
P = Parental (first generation of controlled mating)
F = Filial (each generation resulting from a controlled mating)

9. Compare this to your family:
P1 generation – Your Grandparents
F1 generation – Your Parents
F2 generation – You
F3 generation – Your Offspring

10. The Rule of Unit Factor
Alleles – Alternate form of the same gene, or traits.
Each pea plant had two alleles that determined its height, color, shape, etc…

11. An organism’s alleles are located on two different copies of a chromosome.
One is inherited from the male parent
One is inherited from the female parent

12. The Rule of Dominance Dominant trait: Recessive trait:
The trait that shows up ¾ of the time.
Shown with uppercase letters ~ TT, Tt
Recessive trait:
The trait that shows up ¼ of the time.
Shown with lowercase letters ~ tt

13. Every individual has two alleles of each gene. After meiosis,
The Law of Segregation
Every individual has two alleles of each gene.
After meiosis,
Sperm cells have one allele for a trait
Ovum cells have one allele for a trait
When combined at fertilization you have two alleles for each trait.