Chromosomal-Diseases

= = **Chromosomal Diseases** toc

__ Sex Chromosome Conditions __
Defects affecting the sex chromosomes, usually a man has XY and a woman has XX. All of these examples are caused by non-disjunction where a pair of chromosomes fail to separate during the formation of the egg.


 * **Turner Syndrome**
 * Person has only one X chromosome and no second chromosome
 * Causes sterility and sometimes minor affects
 * People are woman since there is no Y chromosome


 * **Klinefelter Syndrome**
 * Person has XXY chromosomes
 * The person is usually male with lower levels of testosterone
 * Some female-like features because the extra X chromosome
 * Sterility is possible
 * XXXY is possible, may lead to mental retardation


 * **Jacobs Syndrome**
 * Male has an extra Y chromosome XYY
 * Mostly normal
 * May suffer from minor features such as excess male hormones, excessive acne, very tall and aggression


 * **Triple X**
 * Person has extra X chromosome
 * Up to four or five X chromosomes
 * Can be largely unaffected
 * May have infertility
 * May have reduced mental acuity

__ Autosomal Trisonomy Chromosome Diseases __
Occurs when a third copy of an autosomal chromosome is the result of non-disjunction during the formation of the egg. This can occur in males and females.


 * **Down Syndrome**
 * Caused by having an extra third chromosome 21
 * Affects physical features and causes mental retardation


 * **Edwards Syndrome**
 * A third chromosome 18
 * More severe than Down Syndrome
 * Physical defects and mental retardation
 * Often causes early death


 * **Patau Syndrome**
 * A third chromosome 13
 * Very severe mental retardation and physical defects
 * Most babies die soon after birth

__ Monosomy and Autosome Subtraction Disorders __
Occurs when there is only one chromosome or part of the second chromosome is missing which is caused by a deletion mutation that eliminates part of the chromosome completely.


 * **Cri-du-chat (Cat’s cry)**
 * Subtraction of autosome 5, missing part of the second chromosome, but not completely missing
 * Severe mental retardation and physical defects
 * Larynx problems causing the child to have a cat-like cry


 * **Prader-Willi Syndrome and Angelman Syndrome**
 * Different genetic diseases caused on the same chromosome
 * PWS occurs when it happens on the father inherited chromosome copy 15
 * Reduced muscle tone
 * Obesity
 * Small hands and feet
 * Mental subnormality
 * AS occurs on the mother inherited
 * Laughing at anything for no reason
 * Jerky movements and flapping of the hands
 * Peculiar facial expressions
 * Mental Retardation
 * Movement disorders

__ Sources __

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