1. More Inheritance
3.4 continued

2. Traits carried on sex chromosomes
I. Sex-linked Traits
Traits carried on sex chromosomes
Mostly on X, very few on Y
X and Y are not homologous – do not carry the same genes
a. This means females have 2 copies of genes carried on the X chromosome while males only have 1 copy
3. Traits represented as superscripts on the X

3. Because females have two copies, they can be carriers of recessive sex-linked traits (XHXh)
1. If a son receives the recessive allele from mom, he has the recessive trait because he received a Y from dad (XhY)
2. If mom is a carrier, sons have a 50/50 chance of having the trait
3. In order for females to inherit the trait,
their father must have the trait

4. Common Sex-linked traits
1. Color-blindness
2. Duchene muscular dystrophy
3. Calico fur color in cats
4. Hemophilia

5. II. Pedigrees
Used to track traits over generations in a family
1. Circle = females, Squares = males
2. Vertical lines = children, Horizontal lines = “married”
3. Shaded in = expresses the trait being tracked, not shaded in = doesn’t express the trait

6. Often used to track sex-linked traits

7. C. Can be used to deduce mode of inheritance (ex
C. Can be used to deduce mode of inheritance (ex. Is it a dominant or recessive trait?)

8. III. Causes of mutations, genetic diseases, and cancer
Mutagens – external factors that induce mutations
Chemicals, radiation, X-rays, etc. – knock out DNA bases
Carcinogens – mutagens that change genes involved in the control of the cell cycle
Chernobyl
Hiroshima
Marie Curie