Final Exam Flashcards
percentage of pregnancies that have chromosomal anupoloidy
15-20%
most common autosomal aneuploidy
trisomy 16, trisomy 21, trisomy 22
most common sex chromosome aneuploidy
monosomy x (turner syndrome)
with monosomy x, what percentage of fetuses will be aborted
95%
autosomal aneupoloidy in live births, why
trisomy 12, 18, and 21 because heterochromatic regions mostly, so less genes
why is aneupolidy ox sex chromosome less fatal
x chromosome inactivation
down syndrome also called
trisomy 21
trisomy 21 discovered in
1980s
chromosome findings of down syndrome
pure trisomy 95%, translocation 4%, mosaicism 1%
in pure trisomy cases, maternal chromosome non-disjunctions account for _%
90 %
phenotype of down syndrome
upward sloping palpebral fissue, protruding tongue, congenital heart disease (need surgery to repair defective heart)
down syndrome is correlated to an advanced maternal age (35 (+) years old) …what part of cell cycle specifically?
meiosis 1 nondisjunction
Patau syndrome trisomy 13
severe condition, poor prognonsis, severe cleft lip and palate, heart defects in 90% of cases.
incidence 1/5000 newborn babies, most infants due during first few days or weeks of life, correlation with
edward syndrome tisomy 18
1/5000 live birth, incidence at the conception is much higher, but 95% of trisomy 18 fetuses are aborted
severe malformation of the heart
prominent occiput (back of head)
characteristic fists clench, rocker bottom feet,
detect foot with ultrasound
turner syndrome monosomy x
incidence 1/5000 to 1/10000, only seen in females, puffy extremities (edema, too much fluid in tissue of hands and feet), webbed neck, low hair line, widely spaced nipples, 75% of turner pts have maternal x chromosome, therefore the missing sex chromosome is of paternal origin, occurs only in females, (45, x), not severe, abnormal ovaries (no viable eggs, have oval testes, need to be given growth hormone because they are abnormally small,
klinfelter syndrome
additional sex chromosome, 1/1000 male live birth, discovered 1959 (47, XXY), moderate learning difficulties, enlagrement of breats, infertility (100%), increased incidence of carcinoma of breasts in adult life, missing father’s sex chromosome contribution (father meiosis 1 homolog chromosome seperate, where x and y are supposed to seperate but didn’t, so 3 copies in one sperm and one sperm with no sex chromosome)
fragile x syndrome
Martin and Bell 1940s (Martin Bell syndrome), 1/5000 males, 4-8% of all males with learning difficulties, x-linked disease , depression in the female carriers, discovered in 1969, learning difficulties, long face,
