Pedigrees Human Heredity

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

But wait there’s more!! Pedigrees Chromosomes Karyotypes

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.

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

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

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

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

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

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?