Mendelian diseases

1. MENDELIAN DISEASESMENDELIAN DISEASES
TOBIN K DOMINIC

2. INTRODUCTION
Genetic Disorders
 Chromosomal
abnormalities

 Mendelian diseases
 Multifactorial diseases

3. MENDELIAN DISEASES
Definition: Diseases in which the phenotypes are
largely determined by the action, lack of action, of
mutations at individual loci.
Rare 1 % of all live born individuals
4 types of inheritance
:Autosomal dominant
:Autosomal recessive
:X linked dominant
:X linked recessive

5. Offspring has a 50:50 chance of being affected
Both sexes equally affected
Examples
ABO Blood Group System
Retinoblastoma
Neurofibromatosis
Marfans syndrome
Familial polyposis coli

7. Probability 25% (1:4)
Both sexes equally affected
Examples
Hemoglobinopathies: sickle cell anaemia,thalassemia
Inborn errors of metabolism:PKU,Alkaptonuria……
Albinism
Cystic Fibrosis
Hirschsprung disease

9. A mutant gene on X chromosome in males will express itself
readily as there is no normal allele, but a mutant gene on X
chromosome of females will not express itself in the presence
of a normal allele
Examples
Hemophilia
Colour blindness
Duchenne muscular dystrophy
G6PD deficiency

10. X linked dominant affected father

11. Daughters are affected, sons escape
Examples
Vitamin D resistant Rickets
Familial hypophosphatemia
Blood group Xg

12. PREVENTION AND CONTROL
General health promotion
Specific protection
Early diagnosis and Rx
Rehabilitation

13. General health promotion
Eugenics
Euthenics
Genetic counseling
Genetic preventive measures

14. Eugenics
-
+

17. Euthenics

18. Genetic counseling
Prospective
retrospective

19. Preventive measures

20. SPECIFIC PROTECTION

21. EARLY DIAGONOSIS & RX
Detection of carriers
Prenatal diagnosis
Neonatal screening
Recognizing preclinical cases

22. REHABILITATION