A family history of a genetic condition PEDIGREE CHARTS A family history of a genetic condition © 2016 Paul Billiet ODWS

What is a pedigree chart? A record of the family of an individual Used to study the transmission of a hereditary condition Useful when there are large families and a there is a good family record over several generations. © 2016 Paul Billiet ODWS

Studying human genetics Pedigree charts offer an ethical way of studying human genetics Dominant/Recessive Relationships Sex Genotypes Phenotypes A genetic counsellor will still use pedigree charts to help determine the distribution of a disease in an affected family. © 2016 Paul Billiet ODWS

Symbols used in pedigree charts A marriage with five children, two daughters and three sons. The middle son is affected by the condition Normal male Affected male Normal female Affected female Parents Vertical line = Children © 2016 Paul Billiet ODWS

Symbols Completely darkened= homozygous affected Could be dominant or recessive

pedigree chart Generations are identified by Roman numerals. I II III IV © 2016 Paul Billiet ODWS

Identifying Dominant vs Recessive

Tongue rolling (R) © 2016 Paul Billiet ODWS

Tongue rolling rr rr rr rr rr © 2016 Paul Billiet ODWS

Tongue rolling rr Rr Rr Rr rr Rr Rr rr rr Rr rr © 2016 Paul Billiet ODWS

Albinism 1. Dominant or récessive? (A) © 2016 Paul Billiet ODWS

Albinism aa Aa Aa Aa Aa Aa Aa Aa aa aa aa aa © 2016 Paul Billiet ODWS

4 patterns to know Autosomal Dominant Autosomal Recessive Autosomal Sex-linked (X) recessive -There is no (y) transmission

Pattern #1- Autosomal Dominant In general, males & females equally affected NO skipping generations Trait is expressed if allele is present

AD EX: Huntington’s disease Build up of protein causes damage to nerve cells in brain Most people develop symptoms in 40s-50s Symptoms start w/movement problems, slurred speech, balance problems, swallowing difficulties Huntington disease (right) showing a larger cavity where brain cells have died, compared with a normal brain (left).

Pattern #2 – Autosomal Recessive In general, males & females equally affected Can skip generations Both parents are carriers Trait is expressed only if homozygous

AR EX: Cystic Fibrosis Defective chloride-ion transport protein in cell membranes Symptoms – thick, heavy mucus clogs lungs, liver, pancreas Most people do not survive past late 30s Many treatments for symptoms, but NO cure

Pattern #3 - Autosomal In general, males & females equally affected Father-son transmission of trait

Pattern #4 – Sex-linked recessive In general, more males are affected than females If mom is carrier  sons are affected, not daughters If dad is affected  daughters are carriers NO dad-son transmission NO male carriers

EX: Red-Green Color Blindness Affects males more than females 3 types of cone cells working together give you color vision (red, blue, green)

EX: Hemophilia Affects males more than females Missing blood clotting proteins Lots of bleeding from minor cuts Can suffer internal bleeding from bumps/bruises Can be treated w/injections of clotting proteins

Try this one Autosomal dominant

Autosomal Recessive

Dominant Autosomal

Autosomal Recessive

Recessive X linked

Recessive Autosomal

Dominant Autosomal

Autosomal Recessive

X Linked Recessive