Human Pedigrees Drawing and Analysis

Genetic Counseling Helping individuals and prospective parents Your learning gives you the opportunity to determine some probabilities and patterns of inheritance yourself!

Pedigrees A pedigree is a biological family tree that shows the interrelationships between parents and children across generations. Helps illustrate a pattern of inheritance for a single trait through that family Pic of Queen’s Vic. family

Standard Symbols in Pedigrees Male Female Unspecified Gender

Standard Symbols in Pedigrees Clinically Unaffected Clinically Affected Carrier Not Clinically Affected Some pedigrees show phenotype only (no half-shaded boxes; some show genotype (carriers are half-shaded) You will need to determine which system is used in each problem.

Conventions in Drawing Pedigrees Parents Regardless of Social Relationship Male partner on left (usually)

Conventions in Drawing Pedigrees 1 2 II 1 2 3 Full Siblings (in order of age from left to right)

Conventions in Drawing Pedigrees 1 2 II 1 2 3 4 Monozygotic Twins Dizygotic Twins

Conventions in Drawing Pedigrees 1 2 3 Separated Consanguinity II Convention to draw male on lefy but also older relationships/siblings?? Brackets Adopted 1 2 3

Conventions summary

Patterns of Inheritance Dominant: Trait is expressed in every generation – eg. Huntington’s, brown eyes Not seen in offspring unless present in a parent Recessive: Trait may skip generations – eg. TaySachs Sex-Linked: Y linked – only males are clinically affected X linked – affected males more common, may have normal parents, affected females must have affected father

autosomal dominant

Pedigree Practice Autosomal dominant Autosomal recessive X-linked recessive

Pedigree Practice (more rare) D) X-linked dominant E) Y-linked

Pedigree Practice Cardiomyopathy (hypertrophy) Autosomal dominant

Pedigree Practice Warped ear Autosomal recessive

Pedigree Practice Neurofibromatosis Autosomal dominant

Pedigree practice Hemophilia X-linked recessive