1. Pedigrees
Human Heredity

2. What we have covered so far…
Monohybrid crosses
Simple dominance
Incomplete dominance
Co-dominance
Multiple alleles
Sex-linked recessive
Honors- Dihybrid crosses

3. But wait there’s more!!
Pedigrees
Chromosomes
Karyotypes

4. Pedigrees
In humans, scientist’s study a family history using a pedigree.
Pedigree- a diagram that traces the inheritance of a particular trait through several generations.

5. By using boxes, circles and connecting lines, it is possible to diagram a family history of a genetic disease.

6. How to read a Pedigree Circles=females Squares=males
solid objects= diseased individuals
half-solid objects= carriers
unfilled objects= genetically healthy individuals

7. A pedigree also uses a numbering system in which Roman numerals represent generations and the individuals are numbered using 1,2,3,4….

8. Autosomal Inheritance
Sex-Linked Inheritance
affects both men and women
trait is carried on the
X chromosome
affects mostly men
usually recessive
Autosomal Dominant:
- trait usually present in each
generation
Examples: hemophilia,
color blindness, baldness
Autosomal Recessive:
- trait usually skips generations
- will only show up if homozygous

9. How many generations are listed above?
Is the trait above autosomal or X-linked?
Is the trait above dominant or recessive?
How did #8 inherit the trait if his parents don’t express it?
5. Why do sex-linked traits show up mainly in men? 4
Autosomal
Recessive
His parents must be carriers of the trait (heterozygous)
Men have only one X chromosome, and can’t be carriers

10. If individual III-2 marries a person with the same genotype as individual I-1, what is the chance that one of their children will be afflicted with hemophilia?