Understanding a Pedigree Chart A family history of

Understanding a Pedigree Chart A family history of a genetic condition

Quick Review • Genotype = what genes someone has • Genes are usually represented by a letter, a capital letter for the dominant trait, a small case for the recessive. • Example: Tongue Rolling is dominant, so we use R to represent the tongue rolling • Inablility to roll your tongue is recessive so we use r to represent the non-rolling gene • For every trait, you get a gene from each parent

Genotypes and Phenotypes • Mom and Dad are Rr-that is their genotype, they can also be described as heterozygous- they have 1 of each gene • What is their PHENOTYPE? • The youngest son has a genotype of rr-he is Homozygous recessive-2 copies of the recessive gene • His phenotype? I can’t Roll my Tongue!

Some common dominant and recessive traits • Widow’s peak is dominant. • You can be homozygous dominant (WW) or heterozygous (Ww) and you will have widow’s peak • What is your genotype and phenotype if you’re homozygous recessive?

Making a Pedigree Chart • Pedigree charts are made to chart family history and see how traits are passed • A genetic counsellor will use pedigree charts to help determine the distribution of a disease in an affected family

Symbols Draw me • Shade individuals that have the trait you’re studying • Boys = squares (Lucy always calls Charlie Brown a ‘block head’) • Girls = circles

Making a Pedigree Chart • Married-connected at side • Siblings-connected at TOP not at the side (hopefully not siblings AND married) • Oldest child-to the left • Question-if shaded individuals in this pedigree have blue eyes, what is the GENOTYPE of the parents?

Other • Divorced, separated • Deceased • Identical twins • Fraternal twins

Organizing the pedigree chart Generations are identified by Roman numerals I II IV

Organizing the pedigree chart • Individuals in each generation are identified by Arabic numerals numbered from the left • Therefore the affected individuals are II 3, IV 2 and IV 3 I II IV 1 2 3 4 5 6 7

What’s going on? Shaded = blue eyes • 1 and 2 split after having 4, 2 then had kids with 3 and split with her too after 5 -9 were born • Genotypes of 1, 4, 7? • Genotypes of 2 & 3? • Genotypes of 5, 6, 8, 9, 10, 11, 12?

Cleft Chin Pedigree Activity

Make your own pedigree • Using your own family, make your own pedigree chart • Must at LEAST include grandparents, & your generation • Pick one easy dominant or recessive trait and shade individuals that have it. You can guess who has it if you don’t know for sure. (Don’t pick a trait that EVERYONE in your family has) • Label yourself, grandparents, cousins, etc • Put a key on the pedigree so I know what shaded means. Ex. - shaded people have widow’s peak OR…you may create a pedigree chart for a fictional family of your choice. For example, a family in a book you read or a movie you have seen (ex: Twilight series, Harry Potter, etc)