*Unit factors in pairs- genetic characteristics are controlled by unit factors that exist in pairs in individual organisms

1
Review
Unit factors in pairs- genetic characteristics
are controlled by unit factors that exist in
pairs in individual organisms Principle of
Dominance and Recessiveness- one factor is
dominant over the recessive one Law of
Segregation- During gamete formation the paired
unit factors segregate randomly so that each
gamete receives one or the other Law of
Independent Assortment During gamete formation,
segregating pairs of unit factors assort
independently of each other
2
Dihybrid cross
GgWw
3
Dihybrid cross cont
F2
4
The Trihybrid Cross
Trihybrid cross
5
The Forked-Line Method (branch diagram)
Recall The F1 that result from a monohybrid
cross (AA x aa) all have the genotype Aa and the
phenotype represented by A
The F2 that result from a cross between 2
individuals from the F1, have a phenotypic ratio
of 31
6
The Forked-Line Method (branch diagram)
7
The Forked-Line Method (branch diagram)
NOTE We are assuming that independent
assortment of these 3 gene pairs is a random
process!
8
Mendel Rediscovered
Why did Mendels work go unnoticed for so long?
Charles Darwin and Alfred Russel Wallace
continuous variation offspring were a blend
of parents phenotypes
1879 Walter Flemming
early 20th century
1902 Walter Sutton and Theodor Boveri
Chromosomal Theory of Inheritance
9
How do we account for genetic variation?
Cross over
Independent assortment Crossing
over Random
fertilization
Independent Assortment
10
Human Pedigrees
Pedigree
Proband (p)