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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
-
+
Euthenics
Genetic counseling
Prospective
retrospective
Preventive measures
SPECIFIC PROTECTION
EARLY DIAGONOSIS & RX
Detection of carriers
Prenatal diagnosis
Neonatal screening
Recognizing preclinical cases
REHABILITATION