*Gregor Johann Mendel 1822-1884

Chapter 3: Mendelian GeneticsTwo main hypotheses on how traits are transmitted:

*blending inheritance *particulate inheritance

Pisum sativum-Why study (or experiment with) the garden pea?

-Mendel followed several visible features:

The Monohybrid Cross

-Example:

X

Tall Dwarf

P1

F1 – all Tall

F2

Mendel’s Principles of Inheritance*unit factors

1. Unit factors occur in pairs

Tall Dwarf

P1

Factors: DD dd Dd

2. Dominance/Recessiveness

Mendel’s Principles of Inheritance con’t

X

Tall Dwarf

P1

DD dd

F1 – all Tall

TallDd

Mendel’s Principles of Inheritance con’t3. Segregation

DD dd

X

Tall Dwarf

P1

F1 – all Tall

TallDd

D d D dTall Tall

Mendel’s Principles of Inheritance con’tWhat about the F2?

Self cross F1:

ddDD Dd Dd

Four possible combinations result in F2:

1 2 3 4

The Test Cross: One Character-How to distinguish DD or Dd genotype?*Test cross

Punnett Squares

D D d

Tall TallSelf cross F2:Dd Dd

X

Gamete formation: d

CH3 Problem #2:2. Albinism in humans is inherited as a simple recessive trait. Determine the genotypes of the parents and offspring for the following families. When two alternative genotypes are possible, list both. (A) Two non albino (normal) parents have five children, four normal and one albino. (B) A normal male and an albino female have six children, all normal.

Mendelian inheritance is based on probabilityExample- coin toss

The Rule of Addition

Chi-Square Analysis:p value (probability): consider as a percentage (i.e. 0.05 = 5%)

Example from Table 3.1: