1. Pedigree chart
Dr.Rajprasath.R
Senior resident
Department of Anatomy
JIPMER

2. Definition
Diagram of family history indicating normal & affected individuals, their
relationship to the proband & their status with respect to a particular
genetic disorder

3. Symbols used

5. Mendelian Inheritance

6. What is inheritance?
• Passage of genes from parents to offspring
• Pair of genes in 23 pairs of chromosomes
• One of pair goes to one gamete
Chromosome
Gene

7. Single gene disorders
• Due to mutation or change in single gene
• Affected gene is passing to the next generation (inheritance)

8. Types of inheritance
• Based on location & expression of disease
• Autosomal inheritance
• Sex chromosomal inheritance (X-linked)
• Dominant
• Recessive
location
Expression of disease

9. Expression of disease..
• Dominant – only one gene is affected-disease expressed
• Recessive – disease expressed only if both genes are affected
• Symbols indicating

10. - Affected gene
- Normal gene
Disease expressed
Dominant
Disease not expressed
Recessive- carrier
Recessive
Disease expressed
/ Dominant
2
3
1
Homozygotes
Heterozygotes

11. Autosomal inheritance

12. Autosomal dominant
• One or both of the parents are always affected
• 50% chance of children get affected
• Both sexes are equally affected
• All generations are affected
• Normal children do not transmit the disease
• E.g. Achondroplasia
Marfan’s syndrome
Neurofibroma

13. Parents
Gametes
Autosomal dominant inheritance
Affected Affected Unaffected
At
conception

14. How to draw AD
Pedigree chart

16. Autosomal recessive
• Parents are healthy carriers
• 25% chance for children getting affected
• E.g. Cystic fibrosis
Phenylketonuria
Sickle cell disease
Tay-sachs disease

17. Parents
AUTOSOMAL RECESSIVE INHERITANCE
Affected
Unaffected
(carrier)Unaffected
Sperm/Eggs
Unaffected
(carrier)

18. How to draw AR
Pedigree chart

20. Summary
• What is inheritance?
• Different Modes of inheritance
• How to draw a pedigree chart?
• How to diagnose an inheritance pattern from pedigree chart
• Few points about autosomal inheritance

21. THANK YOU