Pedigrees in Human Genetics Ms. Lefebvre SBI3U

Pedigrees in Human Genetics “A diagram that illustrates the patterns of transmission of a trait within a given family.”

Marriage between related individuals Pedigree Symbols Marriage between related individuals

Why Use Pedigrees? Family history of specific genetic disorder 2. An individual with features of a genetic disorder 3. Unexplained abnormalities at birth & childhood disabilities 4. Fetal anomalies or abnormal pregnancy screening tests 5. Planning or confirmed pregnancy between close relatives 6. Multiple pregnancy losses

Some Genetics Humour Some Genetics Humour

Patterns of Inheritance Autosomal Dominant 2. Autosomal Recessive 3. Sex-Linked Disorder

Autosomal Dominant Disorders Affected individuals have affected parent Both sexes will be equally affected About 50% of the offspring will be affected Never skips a generation Ex. Huntington’s Disease

Autosomal Recessive Disorders Both parents are carriers; can produce unaffected offspring Affected individuals may not appear in every generation Males and females are equally affected Ex. Cystic Fibrosis

Sex Linked Inheritance Genetic disorders that are carried on the sex chromosomes, especially the X chromosome.

X-Linked Inheritance

X-Linked Recessive Inheritance Predominantly males affected (passed on from mother) Affected females are extremely rare Traits skip generations Never passed on from father to son Ex. Hemophelia Colour Blindness

Types of Colour Blindness 0.5% of Women 8% of Men and Types of Colour Blindness

#2 = red/green colourblindness What number do you see? #5 = normal vision #2 = red/green colourblindness

#3 = red/green colour vision #8 = normal vision #3 = red/green colour vision No # = total colour blindness #12 = normal vision and any people with colour vision deficiencies

X-Linked Dominant Inheritance Ex. Incontinentia Pigmenti Both males and females can display the trait or disorder The gene is passed from mother to daughter, and, if passed to a son, the pregnancy miscarries Affected males transmit the trait to all of their daughters and none of their sons Ex. Incontinentia Pigmenti

Identify the type of inheritance Autosomal Dominant B. Autosomal Recessive C. X-linked recessive D. X-linked dominant E. Y-linked Identify the type of inheritance

What is it?