Download Multiple Alleles and Polygenic Inheritance

Multiple Alleles and Polygenic Inheritance
Multiple alleles – more than 2 alleles produces 3 or more genotypes.
Examples are Rabbit coat color (4 alleles controlling) and Blood
Types
Blood Types:
Genotypes
Phenotypes
IaIa or Iai
Type A
IbIb or Ibi
Type B
ii
Type O
IaIb
Type AB
Why is blood type important?
Because wrong blood type transfusion can cause death- type O
is the universal donor, type AB is the universal acceptor
Can be used in parentage disputes:
Example: if the mother is type A and the child is AB, can the dad
be type O.
Epistasis:
One allele hides the effects of another allele
Example: Labradors. The dominant allele (E) determines
whether the skin will have pigment. The dominant allele (B)
determines how dark it is.
Genotype
Pigment
eeBb, eebb, eeBB
Yellow
EEbb, Eebb
Chocolate
EEBB, EeBB, EEBb, EeBb
Black
Polygenic Inheritance- more than one pair of genes influencing a
trait.
Examples:
Skin color (approximately 3, but discussion of more)
Eye Color
Height
Sex-linked Traits:
46 chromosomes- 23 pairs (22 pairs of autosomes and 1
pair of sex chromosomes)
In most animals, the sex chromosomes are the X and Y
chromosomes, the Y is smaller.
Male  XY
Female  XX
Father determines the sex of the offspring
Chance is always 50-50 for either sex
X chromosome is longer than Y chromosome
A recessive gene has no matching gene on the Y
chromosome.
In a calico cat, the X’s that control the different colors are
turned on in different cells, reason for the black and
orange pigments.
Se linked disorders are those that are carried on the X
chromosome. For example, red-green colorblindness,
baldness and hemophilia.