1. Advanced Genetics

2. Review Dominant vs. Recessive
If an individual inherits even one dominant allele, that trait will be expressed. BB Bb

3. Continued…
An individual must inherit two copies of a recessive allele for that trait to be expressed. bb

4. Genes Each “recipe” on the DNA is called a gene.
Ex. Hair color and hair texture are two different genes found at different loci (locations) on the
chromosomes.

5. Alleles Example: There is often more than one version for a gene.
These are called alleles.
Example:
Gene = flower color
Alleles = purple or white

6. Beyond Dominant and Recessive Alleles
Not all genes show simple dominant/recessive patterns.
In most organisms, genetics is much more complicated.
The majority of genes have more than two alleles.

7. A. Multiple Alleles
For some genes, there are more than two alleles possible.
For example, for eye color there are alleles for shades of brown, blue, green, and hazel.

8. B. Codominance
If more than one allele is dominant for a trait, they are called codominant.
Both phenotypes will be expressed.

9. Both black and white are dominant in this breed of chicken
Both black and white are dominant in this breed of chicken. A cross results in a chicken that has some black feathers and some white feathers.

10. Red and white fur are both dominant in this breed of cow…
If a cow inherits both (RW), it is described as roan.

11. In humans, blood type is determined by the presence (or absence) of certain antigens (A and B).
These two antigens are codominant.

13. Blood type genotypes
IaIa or Iai– Type A
IbIb or Ibi– Type B
IaIb – Type AB
ii – Type O

14. C. Incomplete dominance
Sometimes, neither allele can dominate the other.
A blend of the traits will appear.
Example: Red and white flowers produce pink offspring when crossed.

16. D. Polygenic Traits
These traits are controlled by more than one gene and have a wide range of phenotypes.
Height
Skin color

17. Define the following vocabulary words…pg 270
Independent assortment
Incomplete dominance
Codominance
Multiple alleles
Polygenic traits