Chromosome Disorders

Prenatal Diagnosis

Amniocentesis A small sample of the amniotic fluid surrounding the baby is removed using a syringe. The fluid contains skin cells from the baby. The skin cells are grown in the lab.

The chromosomes from the cells are magnified under a microscope and a picture is taken. The chromosomes are cut out and arranged in homologous pairs in decreasing size order. This is called a karyotype.

Down Syndrome (Trisomy 21) Extra chromosome 21 in every cell of the body Causes mental retardation, heart defects Karyotype = 47,XX+21 or 47,XY+21

As a woman gets older, her chances of having a baby with a chromosome abnormality increases ***remember, a woman is born with all of her egg cells, but meiosis is not yet complete (egg development stops in prophase I until the follicle matures prior to ovulation)

Most cases of Down syndrome are caused by nondisjunction during meiosis Nondisjunction: homologous chromosomes do not separate properly

http://www. mhhe. com/biosci/genbio/biolink/j_explorations/ch10expl http://www.mhhe.com/biosci/genbio/biolink/j_explorations/ch10expl.htm

Turner Syndrome 45,X Characteristics short stature ovaries do not develop (infertile) cardiovascular problems kidney and thyroid problems skeletal disorders such as scoliosis

Klinefelter Syndrome 47,XXY Characteristics Infertility (cannot produce a lot of sperm) Learning disability

Trisomy 13 severe birth defects mental retardation

Trisomy 18 severe birth defects mental retardation

http://iteachbio. com/Life%20Science/Genetics/Chromosome%20Disorders http://iteachbio.com/Life%20Science/Genetics/Chromosome%20Disorders.ppt