Human Genetics – Studying Chromosomes & Diseases Biology
A picture of a person’s paired chromosomes, arranged in order from largest to smallest Karyotype
Why would a doctor perform a karyotype? If the woman is over 35 (eggs are older) If there are chromosome diseases in the family If a child or adult has symptoms of a chromosome disorder If an adult is having a hard time getting or staying pregnant
Blood samples (for adults or infants) Where do the chromosomes come from?
Chorionic Villi Sampling (for fetus) Cells in the “roots” around the unborn baby are analyzed Where do the chromosomes come from?
Amniocentesis (for fetus) Cells in the fluid around the unborn baby are analyzed
Embryo after cleavage A single cell is removed from the embryo Performed for in vitro fertilization
Problems with Meiosis Chromosomes fail to separate properly Results in too few or too many chromosomes in offspring Often fatal, but some exceptions How do chromosome problems occur?
Trisomy 21 – Downs Syndrome Tri = 3, so Trisomy 21 is 3 chromosome 21’s Mental impairment Upward-slanted eyes Slightly flattened facial features
Trisomy 18 – Edward’s Syndrome Most die before birth; those born die within 2 months Heart abnormalities Difficulty breathing Small in size
die within their first days or weeks of life. five percent to 10 percent of children with this condition live past their first year heart defects brain abnormalities poorly developed eyes extra fingers and/or toes cleft palate weak muscle tone Trisomy 13 – Patau’s Syndrome
Klinefelter Syndrome Males with 2 X chromosomes (XXY) Male appearance Some feminine traits (breasts, higher pitched voice) Sperm count is low Hormone injections can help
Turner’s Syndrome Have single X but no other sex chromosome (XO) Female appearance Tend to be very short Affects sexual development Hormone injections help
Pre implantation Diagnosis A test used prior to implantation to help identify genetic defects within embryos Checks for chromosomal issues before placing the embryo in the mother Can also be used for gender selection