GENETIC DISORDERS

A genetic disorder is a disease that is caused by an abnormality in an individual's DNA. Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes.

Gene Mutations Can either be inherited from a parent or acquired Failure of chromosome pairs to separate properly is called NON-DISJUNCTION Non-disjunction will result in an imbalance of chromosomes Having more or less genetic material is detrimental and is the resulting cause of Genetic Disorders

There are four major types of chromosomal mutations:

#1 DELETIONS: involve deletion of a small portion of a chromosome

#2 DUPLICATIONS: produces an extra exact copy of a specific region of a specific chromosome

#3 INVERSIONS: re-order a segment of chromosome in backwards order Not as detrimental as deletion or insertion

#4 – TRANSLOCATIONS: Occurs when the information from one of two homologous chromosomes breaks and binds to the other Usually this sort of mutation is lethal

In humans, non-disjunction is most often associated with the 21st chromosome, producing a disease known as Down's syndrome (also referred to as trisomy 21).

Sufferers of Down's syndrome display the following characteristics: mild to severe mental retardation short stocky body type Upward slant to the eyes large tongue leading to speech difficulties

Kleinfelter’s Syndrome Males with Kleinfelter’s have an extra X chromosome (XXY) Infertile – do not produce sperm Enlarged breasts Small penis and testicles Sparse facial and body hair

Turner’s Syndrome Missing or damaged X chromosome in females (Momosomy X) Underdeveloped ovaries Short stature, webbed neck Sterile Lacking secondary sexual characteristics

Cystic Fibrosis Hereditary disease primarily affecting the lungs, pancreas and intestines Caused by faulty channel proteins Excess mucous clogs lungs causing a difficulty in breathing, prevents food from being digested Diagnosed with a “sweat test” Life expectancy of patients ~ 36 years

Duchenne’s Muscular Dystrophy Generalized weakness and muscle wasting first affecting hips, pelvic area, thighs and shoulders X linked recessive disorder Eventually even muscles of the lung may weaken which may lead to respiratory failure

Albinism Characterized by little or no pigment in the eyes, skin and hair Major vision problems Inherited altered genes do not make usual amounts of pigment melanin Both parents must carry a defective OCA (oculocutaneous albinism) gene to have a child with albinism

Red-Green Colour Blindness X-linked recessive disorder Person cannot distinguish shades of red and green Visual acuity is normal

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