1. Non-Mendelian and Human Heredity

2. Non-Mendelian Genetics
Essential Questions:
1. What happens when you have two alleles for a trait that are dominant?
2. What is a blended phenotype?
3. If two alleles are dominant, how do I identify which letter to use in the punnett square?

3. Incomplete Dominance Neither allele is completely dominant
When the offspring is heterozygous, a third BLENDED phenotype appears

4. Incomplete Dominance Example
If red flowers (RR) are incompletely dominant to white flowers (R’R’), show the offspring of a cross between 2 pink flowers (RR’)
What is the probability that these two parents will produce pink offspring?
50%
R R’
R R
R R’
R’ R’ R R’
Phenotype ratio:
Red 1, White 1, Pink 2

5. Codominance Both alleles are equally dominant
When the genotype is heterozygous, both phenotypes are represented in an almost equal ratio
Example:
A black cow and a white cow may produce a black and white cow

6. Codominance Example BW B B BB W B
If black chickens (BB) are co-dominant to white chickens (WW), show a cross between a black chicken (BB) and a black and white chicken (BW).
What is the probability that these two chickens will have a white offspring? 0% BW BB W B
Phenotype ratio:
Black 2, black and white 2, white 0

7. Blood Typing – co-dominance and multiple allelism
More than two alleles are available for a trait
Each individual will only have 2 of the alleles
Example: Blood type (3 alleles- A,B,O)
“A” and “B” are co-dominant, “O” is recessive
Genotypes:
TYPE A - IA IA or IA i
TYPE B - IB IB or IB i
TYPE AB - IA IB
TYPE O – i i

8. Sex Linked inheritance
Traits found on the X chromosome
More typical in males
Females: XX Males: XY
Examples of sex linked traits
Color-blindness
Hemophilia
- Male pattern baldness

9. Sex-Linked recessive Color Blindness Hemophilia
One type of this disease (red-green) cannot distinguish between the colors red and green
Hemophilia
Lack a blood clotting enzyme and so cuts and wounds bleed without stopping
If you can see “52” you are normal but if you can only see the “5” then you suffer from red-green color blindness

10. Sex-linkage Example Xb Y Y Xb Xb
A color blind woman (Xb Xb) and a man with normal vision (XBY) want to know what chance a son will have to have normal vision.
What is the probability that these two people will have a color-blind son?
100% XB Xb XB XB Xb Xb Y Xb Y Y
Phenotype:
Both females are carriers (have normal vision but can pass on the trait)
Both males are color-blind

11. Techniques Pedigree Population Sampling Twin Studies
Constructing and analyzing a graphical diagram of one trait over several past generations as well as the current generation
Population Sampling
Study a small randomly selected group to predict patterns in the entire population
Twin Studies
Study identical twins (they have the same DNA) to determine the role environment plays in the expression of our genes
Make a Pedigree of your own family (see pg. 315)
Twin studies and the environmental role they can determine Is on the mini

12. Polygenic Inheritance
More than one gene control a trait
Creates a wide range of phenotypes
Ex. Height, skin color

13. Pedigree
diagram used to track one trait over several past generations as well as the current generation.

14. Karyotypes
The number, shapes, and sizes of the metaphase chromosomes constitute the karyotype
Some genetic abnormalities can be identified using karyotyping (ex. Down syndrome)
Do not need to know thisb

15. Genes vs. Environment
Environment can influence the expression of genes
Ex. Siamese cats fur gets darker in colder temperatures (phenotype changes)
Environmental hazards can create genetic mutations
Called mutagens
ex. UV radiation causes skin cancer
Twin studies are often used to study the influence of the environment on human traits

16. Essential Question
WHY are males more often affected with sex-linked genes?
Because the affected gene is on the X chromosome from the mother, and the father gives the boy a Y chromosome. Therefore the trait is expressed since the father can not give a boy a normal X chromosome. He can only give a boy a Y chromosome.

17. Essential Questions
Which type of inheritance produces a blended phenotype?
Incomplete Dominance
Which type of inheritance produces disorders most often seen in males?
Sex Linkage