Chromosome/Genetic Disorders

Finding Disorders Before Birth After 3 months pregnancy can examine fetus (developing human): Ultrasound—high-frequency sound waves are reflected off the fetus; info translated into a picture

Fetoscopy—slender tube with light inserted into womb to take a look at the baby; gets blood/cell samples

Amniocentesis—fluid removed from surrounding fetus by needle inserted through abdomen

Chronic villus sampling—(CVS); tissue surrounding fetus is examined; surgery

AFP—alfa-fetoprotein—blood test; protein made by fetus; level taken at 15 weeks if low may indicate Down syndrome; or affected by diabetes, race or obesity

Genetic Type of Mutations:  Non-disjunction—in normal meiosis homologous chromosomes separate; second division divide again, problems with second division may not disjoin

Extra chromosome—trisomy Lacks one chromosome—monosomy

Monosomy is more harmful because lacking info Usually sterile

Polyploidy—nucleus does not undergo second meiotic division extra set of chromosomes 3N or 4N --seen in plants; mostly lethal in animals

Kleinfelter’s syndrome (or Klinefleter’s) Disorder occurring due to nondisjunction of the X chromosome. The Sperm containing both X and Y combines with an egg containing the X, results in a male child. The egg may contribute the extra X chromosome.

XXY Males with some development of breast tissue normally seen in females. Little body hair is present, and such person are typically tall, have small testes. Infertility results from absent sperm. Evidence of mental retardation may or may not be present.

Down’s Syndrome Caused by non- disjunction of the 21st chromosome. This means that the individual has a trisomy (3 – 2lst chromosomes).

Down’s Syndrome or Trisomy 21

AUTOSOMAL Disorders Occur on chromosomes other than the 23rd set.

Huntington’s Disease Huntington's disease (HD) is an inherited, degenerative brain disorder which results in an eventual loss of both mental and physical control. The disease is also known as Huntington's chorea. Chorea means "dance-like movements" and refers to the uncontrolled motions often associated with the disease.