1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. One gene determine more than one trait
2. Multifactorial inheritance
Extension to Mendel
1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. One gene determine more than one trait
2. Multifactorial inheritance
Extension to Mendel
1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. Recessive lethal allele
d. One gene determine more than one trait
2. Multifactorial inheritance
Extension to Mendel
Mutations are the source of new alleles
Wild-type allele: frequency more than 1%
Mutant allele: frequency less than 1%
Monomorphic(One wild-type allele)
ABO blood type: polymorphic
agouti
black/yellowblack
1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. Recessive lethal allele
d. One gene determine more than one trait
2. Multifactorial inheritance
Extension to Mendel
1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. Recessive lethal allele
d. One gene determine more than one trait
Extension to Mendel
A single gene determines a number of distinct and seemingly
unrelated characteristics is known as pleiotropy.
Pleiotropy of sickle-cell anemia: dominance relation vary
Cells break down
Oxygen drops
Cells break down before malarial has a chance to reproduce
1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. One gene determine more than one trait
2. Multifactorial inheritance
a. Two genes can interact to determine one trait
b. Heterogeneous trait
c. The same genotype does not always produce the same phenotype
Extension to Mendel
1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. One gene determine more than one trait
2. Multifactorial inheritance
a. Two genes can interact to determine one trait
b. Heterogeneous trait
c. The same genotype does not always produce the same phenotype
Extension to Mendel
Fig. 3.11
How two genes interact to produce novel phenotypes
9:3:3:1, four distinct phenotypes, dihybrid cross of two independent assortment genes
F2 self cross
Fig. 3.12
Complementary gene action
One dominant allele of each of two genes is necessary to producethe phenotypes.
Fig. 3.13
Epistatic: the effect of one gene hides the effect of the other gene
Recessive epistasis
Addition of A or B sugars
H allele is epistatic to the I gene
1. Single-gene inheritance :
a. deviation from complete dominance and recessiveness.
b. Multiple alleles
c. One gene determine more than one trait
2. Multifactorial inheritance
a. Two genes can interact to determine one trait
b. Heterogeneous trait
c. The same genotype does not always produce the same phenotype
Extension to Mendel
The same genotype does not always produce the
same phenotype
1. Modifier genes
2. Environment
Penetrance: occurrence in population
Expressivity: seriousness in the individuals
Modifier genes
Major genes have a large influence, while modifier genes
have a more subtle, secondary effect.
Modifier genes alter the phenotypes produced by the allele
of other genes.
Example: tail length of mouse
T allele: 10%, 50%, 75% of the normal tail-length
The more genes or alleles, the more possible phenotypicclasses, and the greater the similarity to continuous variation
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