GENETIC DISEASES or Hereditary Diseases

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Chromosomal Disorders

Autosomal Diseases

Sex-linked Diseases

Example: Down Syndrome (extra #21 chromosome)

XXY Klinefelter Syndrome

45X Turner Syndrome

Huntington's Chorea- Dominant

Hemophilia- x-linked recessive

Tay-Sachs- Recessive

Sickle-cell anemia (protection against malaria)

Color blindness- x-linked recessive

 Autosomal = Chromosomes that are not sex chromosomes. Out of 46 chromosomes 44 are autosomal. In other words, they deal with body construction.

Sex-linked diseases (Not autosomal) = Sex-linked diseases are X - linked. In other words, the defective genes are only found on the X-chromosomes. Out of 46 chromosomes, 44 are autosomal. The remaining 2 chromosomes are sex chromosomes. 

Sex-linked Recessive Diseases

Hemophilia & Color Blindness

XN XN = Normal female


XN Xn = Normal female carrier

XN Y = Normal male

Xn Xn = affected female

Xn Y = Affected male


Chromosomal Disorders:

Down Syndrome/ Trisomy 21: Having an extra chromosome for the 21st pair causes Downs syndrome. The disorder results in mild to moderate retardation, heart defects, hyper-flexibility of joints etc… The longer women wait to have children, the greater the chances of having a down's baby. It is difficult to tell how severely a child will be affected if a Downs baby is diagnosed during pregnancy. This disorder is the result of non-disjunction, which can occur during the formation of gametes during meiosis.

 Sex Chromosomes Disorders.

Turner's syndrome: XO- normal intelligence. Under-developed ovaries, abnormal jaws, webbed necks, shield-like chests.

XXY- Klinefelter Syndrome: Tall and infertile. Behavioral and speech problems.


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