*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 factors1. 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
Sample Problem:
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%)