1. Variations of Inheritance
Chapter 10.3
Variations of Inheritance

2. Intermediate Inheritance

3. Sometimes neither allele is dominant, so the offspring are a mixture
intermediate inheritance– mix of alleles
Ex. Andalusian chickens
NOT BLENDING

4. Multiple Alleles

5. Sometimes there are more than just 2 alleles
Example is blood type with A, B, and O
They get written as IA, IB, i (with A and B being dominant to O)
codominant – when dominant alleles share expression, like blood type AB (IA and IB)

7. Polygenic Inheritance

8. Examples are height and skin color Example:
If multiple genes affect a phenotype, it is called polygenic inheritance
Examples are height and skin color
Example:
3 genes for height
A, B, C are tall
a, b, c are short.
You can be AABBCC and be tall, AaBBCC is less tall, AaBbCC is less tall, etc.
Some characteristics – dozens of genes

9. Importance of Environment

10. The environment can affect the phenotype of genes
leaves on a plant – might change every season based on conditions
identical twins – may have different physical activity, medical history, exposure to sunlight, etc.

11. Concept Check 10.3 Question 1
For a trait with intermediate inheritance, what is the phenotypic ratio for F2 offspring of a monohybrid cross? How is that different from a simple dominant-recessive cross?

12. Concept Check 10.3 Answer 1 1 : 2 : 1
In a simple dominant-recessive cross the phenotypic ratio would be 3 : 1.

13. Concept Check 10.3 Question 2
Two parents have type O blood. What blood type would you expect for their first child?

14. Concept Check 10.3 Answer 2
Type O

15. Concept Check 10.3 Question 3
What is the likely mechanism of inheritance for a characteristic with a large range of phenotypes? Explain.

16. Concept Check 10.3 Answer 3 Polygenic inheritance
The potential combinations of alleles increase with the number of genes affecting a characteristic.

17. Concept Check 10.3 Question 4
Give three examples of human physical characteristics affected by the environment.

18. Concept Check 10.3 Answer 4
Height, build, shade of skin, blood count