BME 80H Lecture Notes - Lecture 19: Robertsonian Translocation, Patau Syndrome, Down Syndrome
11 Jun 2018
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19th lecture
--Fertilization results in either a
monosomy (n-1) + n = 2n-1
trisomy (n+1) + n = 2n +1
2. Autosomal Aneuploidy
Monosomy
- Result in spontaneous abortion
Trisomy
- sometimes viable, most are lethal
- 40% are trisomies of 13-15, 21 and 22
(acrocentric) (figure 6.15/NA, use figure
6.15 handout)
- 1/3 are trisomies of chromosome 16 which is not compatible
with life
a) Viable autosomal trisomies (Handout)
- do not survive to adulthood: trisomy 13, 18
Trisomy 13: Patau Syndrome (47, + 13)
- mean survival = 6 months
- Extra copy of chromosome 13
- Present in about 1/15,000 births
- Can result from a parent with a 13, 14 Robertsonian
translocation
find more resources at oneclass.com
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Document Summary
-fertilization results in either a monosomy (n-1) + n = 2n-1 trisomy (n+1) + n = 2n +1: autosomal aneuploidy. 40% are trisomies of 13-15, 21 and 22 (acrocentric) (figure 6. 15/na, use figure. 1/3 are trisomies of chromosome 16 which is not compatible with life: viable autosomal trisomies (handout) Do not survive to adulthood: trisomy 13, 18. Can result from a parent with a 13, 14 robertsonian translocation. Trisomy 21: down"s syndrome (47, +21) (figure 6. 18) Not considered heritable and that is because it occurs during nondisjunction, which is an error in meiosis. Rarely is inherited from a carrier of a translocation involving chromosome 21: maternal age and risk for autosomal trisomies. (figure 6. 19, handout: spermatogenesis, table. After 35 years if age, there are about 1/3 pregnancies that are trisomic. Mostly result from maternal nondisjunction (in meiosis i). Female meiosis (oogenesis): a closer look (handout: oogenesis) Mitosis yields the primary oocyte (before birth).
