1. Pioneer of Genetics: Gregor Mendel
Gregor Mendel was an Austrian monk whose experiments with garden peas laid the foundation for the science of genetics
Mendel’s work provided a basis for understanding heredity

2. Why did Mendel choose the garden pea?
Identifiable characteristics
Page 130, Fig 2
Plant reproduction: self and cross-fertilizing

3. Plant reproduction Male – Stamen Female – Carpel
Fertilization occurs when pollen produced by the stamen attaches to the carpel, this is known as pollination

4. Mendel cross-pollinated the pea plants
Started with pure breeding plants – those that only produce identical offspring. Ex) tall plants only produce other tall plants

5. The first generation was all purple!
The purple trait masked the white flower trait!
F1 generation or first filial

6. Mendel’s explanation
He called the purple trait dominant because it masked the white trait. He represented it with a capital P
He called the white trait recessive and represented it with a lower case p
Each copy of the trait (gene) is called an allele, one allele comes from each parent. These alleles separate, or segregate, during the formation of sex cells.

7. Some more terminology
Genotype refers to the alleles an organism contains for a particular trait (Pp)
Phenotype refers to the observable trait (purple)
Homozygous: a genotype in which the alleles of a pair are the same
Heterozygous: a genotype in which the alleles of a pair are different
Monohybrid cross: a cross that involves only one trait

8. Mendel created a second generation by allowing the F1s to self-pollinate
F1 generation
Pp Pp
Meiosis occurs. Each gamete has one of the homologous chromosomes.
P p P p PP
Purple Pp
Purple Pp
Purple pp
White
F2 generation inherits alleles from the gametes of the F1
75% purple, 25% white

9. Cross simulation using Punnett squares
Cross 1 (pure breeding plants)
White parent pp p P
Gametes Pp
Phenotypic Ratio
100% purple PP
Purple parent

10. Cross simulation using Punnett squares
Cross 2 (self pollination)
Purple parent Pp P p
Gametes PP Pp
Phenotypic Ratio
75% purple 25% white Pp Pp pp
Purple parent

11. Mendel’s Laws of Inheritance
Each parent contributes one allele. If a pure-breeding plant self-fertilizes, each offspring receives two copies of the same allele.
Dominant alleles are always expressed when a recessive allele is present.
Each pair of alleles segregates during the formation of sex cells.