1. Inheritance Patterns
Mendelian and Complex

2. I. Simple Recessive Disorders
A. Cystic Fibrosis
1. accumulation of thick mucus in the lungs and digestive tract
2. person’s affect literally can drown in their own mucus

3. Cystic Fibrosis

4. I. Simple Recessive Disorders
B . Tay-Sachs Disease
1. lack of an enzyme that breaks down lipids created in the brain
2. fat builds up in the brain, destroys brain tissue – baby dies by age of 2

5. Tay-Sachs Disease

6. I. Simple Recessive Disorders
C. Phenylketonuria (PKU)
1. person lacks enzyme (phenylalanine hydroxylase ) that breaks down the amino acid phenylalanine
2. amino acid builds up and damages nervous system

7. II. Simple Dominant Disorders
A. Huntington’s Disease
1. caused by a DOMINANT allele – only have to have one copy to get the disease
2. causes holes in the brain where tissue has been broken down

8. phenylalanine hydroxylase

9. Normal Brain with Tumor

10. Huntington’s Disease

11. III. Complex Inheritance Patterns
A. Incomplete Dominance
1. type of inheritance pattern where the recessive and dominant phenotype are blended together

12. III. Complex Inheritance Patterns
Example: Red Snapdragons
x White Snapdragons
Red (RR) x White (R`R`)
Pink (RR`)
* because the recessive trait appears to be stronger, we won’t write it as “r” – designate as R`

13. Incomplete Dominance

14. Incomplete Dominance
R R R`

15. Incomplete Dominance
R R
R` RR` RR`

16. III. Complex Inheritance Patterns
B. Co-dominance
1. situation where BOTH alleles are equally dominant
2. both alleles expressed equally – not blended

17. Co-Dominance P Generation: Black-feathered Chicken x
White-feathered Chicken
F1 Generation:
Checkered Chickens

18. Co-Dominance
B B W

19. Co-Dominance
B B
W BW BW

20. Checkered Chicken

21. III. Complex Inheritance Patterns
C. Multiple Alleles
1. trait that has more than 2 alleles
2. Blood Types
a. IA, IB, i
b. A, B, AB, and O

22. Blood Type Chart

23. III. Complex Inheritance Patterns
D. Sex-Linked Inheritance
1. normal traits found on sex chromosome are ONLY found on the X
2. Females require 2 copies (XX) for the trait – males only require 1 copy (XY)

24. Colorblindness Normal Vision Allele: XB Colorblindness Allele: Xb
Let’s say Mom is a normal vision person who is homozygous dominant for the normal vision allele.
Her Genotype is: XBXB
Let’s say Dad is colorblind: XbY

25. Colorblindness
If they have another child, what are the chances that they will have a colorblind boy?
P1 XBXB x XbY

26. Colorblindness
XB XB Xb Y

27. Colorblindness
XB XB
Xb XBXb XBXb
Y XBY XBY

28. Colorblind Tests Everyone should be able to see the circle, square,
and star

29. Colorblind Tests
Colorblind people ONLY see the
yellow square.

30. Colorblind Tests
Colorblind people ONLY see the
yellow circle.

31. Colorblind Tests

32. What Colorblind People See