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MAJOR GENETIC DISORDERS

PUBLISHED BY: SURENDER KUMAR
DECEMBER 18, 2012

   
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 MAJOR GENETIC DISORDERS

DOWNS' SYNDROME ( a k a Mongoloid Idiocy Or Mongloid Syndrome)

Caused by the trisomy (three chromosomes) of the 21st chromosome, creating a total of 47 chromo­somes instead of 46. It is characterized by a round face, broad forehead, projecting lower lip, short neck, stubby fingers, etc.

 

 PHENYLKETUNORIA (PKU)

Causes a deficiency of an enzyme called phenylalanine in the liver. The body cannot digest certain essential proteins due to this deficiency and they keep on getting deposited in the body. Marked by mental retardation, hypopigmentation of skin and hair, eczema.

 

HAEMOPHILIA

A recessive gene trait which occurs due to the absence of thromboplastin or anti-haemophilia globulin. The blood cannot clot in case of even a minor injury.

 

ABO INCOMPATIBILITY

The mothers with blood group O possess neither antigen A nor B but rather have anti-A and anti-B antibodies. The A or B group antibodies of the mother cause partial destruction of RBCs and the production of billirubin (causing mild anaemia and jaundice in the baby’s body). Similarly, the A-group foetus in a B-group mother is attacked by the mother’s antibodies. The ABO hemolytic (RBC-destroying) disease of the newborn is quite common but less severe as compared to Rh-incompatibility.

 

THALLASEMIA

Caused by a pair of recessive genes, results from a defec­tive synthesis of haemoglobin. Causes excess of iron in the body, which deposits in the liver.

 

SICKLE CELL ANAEMIA 

Caused by a recessive gene that causes abnormalities in haemoglobin resulting in sickle cell RBCs (rigid sickle cells obstructing the capillary blood flow).

 

 

COLOUR BLINDNESS 

 

Renders one unable to distinguish between two colours, mostly red and green. Though carried by females, it is mostly exhibited by males only. Similar to baldness in terms of gentic expression.

 

 

 

 



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