1. Non-Mendelian Genetics

2. Linked Genes
Genes for 2 traits are located on the same chromosome and travel together into the same gamete P L p l

3. Crossing Over
New combinations of alleles in the offspring that occur when neighboring segments of tetrads break off where they meet and exchange genetic material

4. Sex-Linked Genes X-linked Genes: genes found only on the X chromosome
Y-linked Genes: genes found only on the Y chromosome

5. X-Linked Genes
Many hereditary diseases are X-linked, meaning the gene is found on the X chromosome
Ex: red-green color blindness
hemophilia x x x XX XX Y XY XY
XX= normal female
XX= carrier female
XY= normal male
XY= affected male

6. Test for Red-Green Color Blindness

7. Sex-Limited Traits
Expressed only in the presence of sex hormones and are only observed in one sex or the other
Controlled by genes not found on the sex chromosomes
Although both males and females have these genes, they are only expressed by one sex since the appropriate sex hormone must be present
EX: color in birds
beard growth in human males

8. Sex-Influenced Traits
Expressed in both sexes, but they are expressed differently
EX: Baldness
In the presence of the male sex hormone, the allele is dominant
In the presence of the female sex hormone, the allele is recessive

9. Intermediate Inheritance
The heterozygous offspring have traits that are not exactly like the trait of either purebred parent
There are 3 types of intermediate inheritance:
Incomplete Dominance
Codominance
Polygenic Inheritance

10. Incomplete Dominance
In the heterozygous offspring, the dominant allele does not completely mask the effect of the recessive gene
The offspring shows a phenotype that is in between the phenotype of the two homozygous parents

11. Example of Incomplete Dominance

12. Codominance Both alleles in the heterozygote express themselves fully
Ex: Blood Types
The IA & IB genes are both dominant, so if an individual has one of each of these genes, their blood type is AB
The iO gene is recessive
EX: Feather Color
White (WW) and Black (BB) are both dominant, so a cross between a white chicken and a black rooster will produce a speckled offspring (BW)

13. Inheritance by Multiple Alleles
When there are more than two alleles in a population, these genes are said to have multiple alleles
EX: blood type—there are 3 alleles in the population: IA, IB & iO
Possible combinations:
Possible Genotypes
IA IA
IA iO
IB IB
IB iO
IA IB
iO iO
Blood Types
Type A
Type B
Type AB
Type O

14. Polygenic Inheritance
Some traits are controlled by 2 or more genes
EX: eye color

15. Pleiotrophy When a single gene affects more than one trait
EX: sickle cell anemia
Changes the cell shape
Causes anemia
Causes brain damage
Causes spleen damage
Causes heart damage

16. Body Temperature and Gene Expression
In some organisms, body temperature can affect the expression of genes
EX: Himalayan rabbit’s coat color
The colder body parts (i.e. feet, ears, nose) are black
The warmer body parts are white