MENDELIAN DISEASESMENDELIAN DISEASES

TOBIN K DOMINIC

INTRODUCTION

Genetic Disorders

Chromosomal abnormalities

Mendelian diseases

Multifactorial diseases

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

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

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

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

X linked dominant affected father

Daughters are affected, sons escape

Examples

Vitamin D resistant Rickets

Familial hypophosphatemia

Blood group Xg

PREVENTION AND CONTROL

General health promotion

Specific protection

Early diagnosis and Rx

Rehabilitation

General health promotionEugenicsEuthenicsGenetic counselingGenetic preventive measures

Eugenics

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Euthenics

Genetic counseling

Prospective

retrospective

Preventive measures

SPECIFIC PROTECTION

EARLY DIAGONOSIS & RX

Detection of carriers

Prenatal diagnosis

Neonatal screening

Recognizing preclinical cases

REHABILITATION