A family history of a genetic condition 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? Rr Rr Rr Rr Rr rr

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

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 III IV

Organising the pedigree chart Individuals in each generation are identified by Arabic numerals numbered from the left Therefore the affected individuals are II3, IV2 and IV3 I II III 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? bb, Bb, and could be BB or Bb. In what generation are there twins?

Time to Practice…