PEDIGREE CHARTS A family history of a genetic

PEDIGREE CHARTS 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? (Roller or non-roller? ) • The youngest son has a genotype of rr-he is Homozygous recessive-2 copies of the recessive gene • His phenotype?

What is a pedigree chart? • Pedigree charts show a record of the family of an individual • They can be used to study the transmission of a hereditary condition • They are particularly useful when there are large families and a good family record over several generations.

Studying human genetics • Pedigree charts offer an ethical way of studying human genetics • Today genetic engineering has new tools to offer to doctors studying genetic diseases • A genetic counsellor will still use pedigree charts to help determine • the distribution of a disease in an affected family

Symbols used in pedigree charts Normal male Affected male A marriage with five children, two daughters and three sons. The next to eldest son is affected by the condition. Normal female Affected female Marriage Eldest child Youngest child

Symbols • Shaded individuals have the trait you’re studying • Boys = squares • Girls = circles

• Married-connected at side • Siblings-connected at TOP not at the side • Oldest child-to the left • Question-if shaded individuals in this pedigree have blue eyes, what is the GENOTYPE of the parents?

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

Organising the pedigree chart • A pedigree chart of a family showing 20 individuals

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

Organising 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 1 2 3 4 5 6 7 II IV

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?

Time to Practice…