Genetic Changes Mutations Karyotypes

Chromosomal Abnormailities Missing piece or whole chromosome Monosomy Extra piece or whole chromosome Trisomy

Turner Syndrome – also called 45,X Caused by a monosomy of the X chromosome Female but are typically shorter No sexual maturation

Down Syndrome – all called trisomy 21 Caused by an extra chromosome 21. Symptoms: mental retardation, small head, flat nose, protruding tongue, upward slanting eyes Frequently there are other internal abnormalities (heart problems) Women who give birth after 35 increase their chances.

Trisomy –X Syndrome – also called 47,XXX Trisomy of 23rd pair (sex chromosomes) Women with an extra X chromosome Most are normal, ◦some mild mental retardation.

Double-Y Syndrome – also called 47, XYY Trisomy 23 Men with extra Y chromosome Tend to be tall but mostly normal May have some violent tendencies

Klinefelters Syndrome – also called 47, XXY Male Tend to be tall but Do not undergo normal sexual maturation - sterile May have enlargement of the breasts

What causes chromosomal abnormalities? Nondisjunction - is the failure of chromosome pairs to separate properly during meiosis ◦Can happen in Meiosis I or Meiosis II Pearson Success Net Activity 12.2 Pearson Success Net Activity 12.2

How do we diagnose chromosomal abnormalities? Karyotype - A picture of all of a person’s chromosomes Help geneticists to see extra or missing chromosomes Pearson Success Net 9.5 Pearson Success Net 9.5

TOK The quad screen test is a maternal blood screening test that looks for four specific substances: AFP, hCG, Estriol, and Inhibin-A. ◦AFP: alpha-fetoprotein is a protein that is produced by the fetus ◦hCG: human chorionic gonadotropin is a hormone produced within the placenta ◦Estriol: estriol is an estrogen produced by both the fetus and the placenta ◦Inhibin-A: inhibin-A is a protein produced by the placenta and ovaries

TOK High levels of AFP ◦may suggest that the developing baby has a neural tube defect such as spina bifida or anencephalyspina bifida ◦most common reason for elevated AFP levels is inaccurate dating of the pregnancy Low levels of AFP and abnormal levels of hCG and estriol ◦may indicate that the developing baby has a trisomy or another type of chromosome abnormality.

TOK Quad screens are fairly noninvasive, amniocentesis or CVS is very invasive and can actually cause spontaneous abortion Who should decide when a karyotype is necessary? Who should decide whether to keep or abort the fetus which presents with chromosomal anomalies? In the U.S.A. it is legal to terminate a pregnancy if it is discovered the fetus has a chromosomal anomaly. Who should be in charge of establishing these laws? Karyotyping can also be done to determine the gender of the fetus. Should this be allowed, especially considering countries where they have child birth restrictions (China)?