A family history of genetics PEDIGREE CHARTS A family history of genetics Edited from the original produced by Paul Billiet [http://www.saburchill.com/IBbiology/bio_hp.html]

What is a pedigree chart? a diagram that shows the appearance of a particular gene from one generation to the next can be used to study the inheritance of a hereditary condition (like cystic fibrosis) are particularly useful when there are large families and a good family record over several generations.

Symbols Used in Pedigree Charts A marriage with five children, two daughters and three sons. male female Vertical lines connect children to their parents A solid square or circle indicates that the person has a certain trait Oldest child  Youngest child A half-filled square or circle indicates that the person is a carrier of the trait.

Organizing the Pedigree Chart A pedigree chart of a family showing 20 individuals

Organizing the Pedigree Chart Generations are identified by Roman numerals I II III IV

Organizing the Pedigree Chart Individuals in each generation are identified by Arabic numerals numbered from the left I II III IV 1 2 1 2 3 4 5 6 7 1 2 3 4 5 6 1 2 3 4 5

Organizing the Pedigree Chart In this example, let’s look at a recessive trait like light eyes. Individuals II3, II6, IV2, and IV3 have light eyes. The carriers (of the recessive gene) are I1, I2, III5, and III6. I II III IV 2 1 3 4 5 6 7