It mainly describes three diseases Duchnne Muscular dystrophy SCID Sickle Cell Anemia

1. Genetic Diseases
By
Dr Archna Sahay

2. 1. Introduction
2. Duchenne Muscular Dystrophy
3. Severe Combined Immnodeficiency
4. Sickle Cell Anemia

3. Introduction
 Genes carry information for heredity in the form of DNA
that passes from parents to child.
 Genetic disease caused by change or mutation in the
sequence of DNA.
 Genetic diseases divided into three categories
1. Single gene disorder:
Caused by defect in one particular gene. They are
a. Dominant: When individual has one copy of altered gene
Example-Huntington’s disease

4. b. Recessive: When individual has two altered version of
genes.
Example- Cystic fibrosis
c. X-linked disorder: In this the altered gene is present on X
chromosome. It mainly affects males. Female acts as carrier.
Example-Muscular dystrophy
2. Chromosomal disorder: It is due to change in number or
strcture of the chromosome.
Downs syndrome: Results due to trisomy of chromosome 21
3. Multifactorial disorder:
It is caused by change in multiple genes. Environmental and
life style factors also affect it

5. 1.Duchenne Muscular
Dystrophy
 It is X linked genetic disorder.
 It is named after the French neurologist B. A Duchnne
who discovered it in 1860.
 It lead to muscle degeneration that results to paralysis and
death.
 This disease is due to mutation in dystrophin gene.
 It mainly affects mans and females act as carrier .

6. DMD gene code dystrophin protein that is structural
component within muscle and tissues.
Dystrophin protein provide stability to dystroglycan complex
(DGC) located in cell membrane.
Because of this attachment of muscle fiber to extracellular
matrix become weaken.
Now scar tissue that is mixture of blood vessel and collagen
replace muscle fiber. It leads to increased muscle rigidity.

7.  The symptoms appears at the age of 6 year. Weakness spread
in arm and neck region.
 This leads to difficulty in standing and abnormal bone
development. It results skeletal deformities.
 Life span: it range from Teen age to mid 30’s.
 Detection
1.CPK Test: Creatin phosphokinase leaks in blood stream.
CPK level rises in blood.
2. Prenatal test: can be performed in 10-12 weeks by chorion
villus sampling.

8. 2. SCID
Severe combined immunodeficiency
 In this genetic disease neither cell mediated immunity nor
humoral immunity works.
 Thus microbial infection leads to death of the person.
 in this disease gene encoding adenosine deaminase (ADA)
becomes defective.
 Normal catabolism of purine becomes defective that was
toxic for T and B cell.
 Treatment:
1.Provide germ free environment to person
2. ADA extracted from cows can be administered

9. 3. Sickle Cell Anemia
 Hb Consist of four subunits, two alpha-globin
subunit and two beta-globin subunit.
 HBB Gene provide instruction to form beta-globin
gene that become defective in this disease.
 In this disease beta globin subunit replaced by Hb
S.
 Characteristic symptom of the disease is low
number of RBC.
 The red blood cell becomes sickle shape and break.

10.  Symptoms: This disease leads to shortness of
breath, fatigue and delayed growth and
development in children.
 It may result organ damage due to deprived
oxygen.
 This disease follows autosomal recessive pattern.

11. Thank You