1. Pedigrees in Human Genetics
Ms. Lefebvre
SBI3U

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

3. Marriage between related individuals
Pedigree Symbols
Marriage between related individuals

4. 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

5. Some Genetics Humour
Some Genetics Humour

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

7. 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

8. 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

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

10. X-Linked Inheritance

11. 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

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

13. #2 = red/green colourblindness
What number do you see?
#5 = normal vision
#2 = red/green colourblindness

14. #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

16. 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

17. 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

18. What is it?