Mendel’s Contribution(s)?
Mendel’s First Postulate
Unit Factors in Pairs
 Genetic characteristics are controlled by unit factors
that exist in pairs in individual organisms,
 each individual receives one unit factor from each
parent,
 in a monohybrid cross, three combinations of unit
factors are possible,
Mendel’s Second Postulate
Dominant/Recessive
 When two unlike unit factors are present in a single
individual, one unit factor is dominant to the other,
which is said to be recessive.
Mendel’s Third Postulate
Segregation

During the processes of heredity, the paired unit
factors separate so that the offspring receives one
unit factor from each parent,

The unit factors segregate to offspring randomly.
Mendel’s Forth Postulate
Independent Assortment
 How do two traits segregate in the offspring of an
individual that is heterozygous for both traits?
Forked-Line Method
Haplo/Diplo and complementation
1. Both recessive:
aaDD x Ad  female: AaDd, male aD
2. Both Dominant: aaDD x Ad  female: AaDd, male aD
3. One dominant*: aadd x AD  female: AaDd, male ad
or…
AADD x ad  female: AaDd, male AD
dominant!
* need to define which is
Forked-Line Method
Haplo/Diplo
AaDd
1/2 A
1/2 a
½D
1/2 x 1/2 = 1/4 AD
½d
1/2 x 1/2 = 1/4 Ad
1/2 D
1/2 x 1/2 = 1/4 aD
½d
1/2 x 1/2 = 1/4 ad
Forked-Line Method
Haplo/Diplo
AaDd x AD* (*male genotype could be ad, aD, Ad)
1/2 A
1/2 a
½D
1/2 x 1/2 = 1/4 AD
1 AD = ¼ ADAD
½d
1/2 x 1/2 = 1/4 Ad
1 AD = ¼ AdAD
1/2 D
1/2 x 1/2 = 1/4 aD
1 AD = ¼ aDAD
½d
1/2 x 1/2 = 1/4 ad
1 AD = ¼ adAD
Lab
Life Cycles
Wasp Development
Timelines
o
o
18 , 28 C
C. elegans
Nomenclature
Tower of Babel