1. HUMAN CHROMOSOMES Chapter 14-2
Genes located on sex chromosomes follow different patterns of heredity.  Males are more likely to be affected by these genes. 

2. GENES ARE LOCATED ON CHROMOSOMES
Some genes are located on the SEX CHROMOSOMES  ( X and Y)
Genes on the X chromosome may affect boys different from girls
These are called SEX-LINKED GENES

3. EXAMPLES: SEX LINKED GENES
Coat color in cats:  Black, Orange,  Calico
X B X B  = black, female
X O X O = orange, female
X B X O = calico, female
X B Y  = black, male
X O Y  = orange, male
REMEMBER:  THE Y IS WIMPY!  No letters (genes) are attached to it.

4. X B X B (black female) x X O Y (orange male)
CROSSES
X B X B  (black female)      x     X O Y  (orange  male) 
This explains why all calico cats are female!
ALSO:  in any given cell, one of the X's becomes inactive, which randomizes the pattern or orange and black

5. COLORBLINDNESS IS ALSO SEX LINKED
Look what happens when a woman who is a CARRIER (b) marries a normal man (B)
X B X b     x      X B Y
What happens when a colorblind man marries a normal woman?
X B X B     x      X b Y

6. COLORBLIND TEST

7. Young children are given pictures instead of numbers

8. HEMOPHILIA  - "bleeder's disease"
Blood will not clot normally, small injuries can be life threatening
Females can be carriers:  

9. What happens if Mom is a carrier?

12. DUCHENNE MUSCULAR DYSTROPHY
- causes progressive weakening and loss of muscle tissue
Females can be carriers:                          X D X d