Download Mendelian Genetics

Genetics
I. Mendelian
A. Introduction
1. History
a. C. Darwin & A. Wallace
proposed blending
b. In 1860, G. Mendel & F. Unger
proposed mixing
B. Experimental Design
1. Monohybrid Cross
a. Definition
b. Terms
i. Self vs. Cross Fertilization
ii. Traits vs. Characteristics
c. Process
Figure 10.1
Figure 10.2
i. Outcomes for a one trait cross or a Monohybrid cross
ii. Principle  All traits are paired and sorted into gametes
Figure 10.3
d. Terms
i. Gene versus Allele
ii. Homozygous versus Heterozygous
iii. Dominance versus Recessive
iv. Genotype versus Phenotype
e. Testcross
What are the parental genotypes?
Figure 10.4
2. Dihybrid Cross
a. Definition
b. Process
Always start these crossing questions by figuring out the parents and then
how many and what type of gametes are produced.
Figure 10.6
i. Outcomes
AaBb
X AaBb
Dihybrid Heterozygous cross Both
Parents
are AaBb
Gametes = AB, Ab, aB, & ab for both parents
Phenotypic ratio= 9:3:3:1 & Genotypic ratio= 1:1:2:2:4:2:2:1:1
Dihybrid Heterozygous cross with a Homozygous Dominant
Parents are AaBb X AABB
Gametes AaBb = AB, Ab, aB, & ab; AABB= AB only
Phenotypic ratio = all dominant, Genotypic ratio = 1:1:1:1
ii. Principle  Each pair of alleles and
chromosomes sort independently into gametes.
II. Variation on Mendel
A. Incomplete Dominance
Appears to be a blending of the two alleles vs. complete
dominant.
Figure 10.6
B. Co-Dominance
AA
aa
Aa
Expression of alleles yields both traits in heterozygote.
C. Multiple Alleles
Figure 10.17
Multiple alleles are needed to give the expression of
the trait.
D. Penetrance
The timing of expression of traits in the phenotype.
E. Gene Interactions
1. Pleitrophy
2. Polygenic
Figure 10.21
One gene causing many
different effects
Figure 10.18
Continuous Variation of
Expression of traits
3. Epistasis
Interference of expression
between different genes
Just to make sure you can tell
the difference.
III. Classical Genetics
A. History
1. W. Bateson & R. Punnett (1908) Punnett Square
2. T. Morgan (early 1900’s) used fruit flies WHY?
Recombination experiments
Developed karyotyping techniques,
Figure 13.7
linkage group studies,
Figure 9.4
& sex linkage studies.
Figure 10.24
3. A. Sturtevant
a. mapping
V. Detection of Problems
A. Karyotyping
How?
B. Amniocentesis  Cellular
and Chemical Analysis
Figure 13.8
C. Ultrasound gives a sound (visual) image of the fetus.
D. Chorionic Villi Sampling== placenta samples
E. Fetal Tissue Sampling
F. Pedigrees == familial history
Figure 10.9
Figure 10.10
Figure 10.25