Only a small fraction of human fetuses with trisomy 18 survive to birth, and mos
ID: 64977 • Letter: O
Question
Only a small fraction of human fetuses with trisomy 18 survive to birth, and most surviving trisomy 18 newborns die in infancy. You prepared DNA samples from umbilical cord blood of a newborn baby with trisomy 18, as well as from his parents’ blood. You then typed the baby and his parents for three microsatellite markers (Str1, Str2, Str3) that are distributed along chromosome 18 (as indicated on the chr.18 map). A diagram of the electrophoresis pattern of your PCR -amplified DNA samples is shown below the pedigree of this family.
In which division of meiosis did nondisjunction occur?
In this case of trisomy 18, how many chromosomes would have been present in the first polar body?
In this case of trisomy 18, how many chromosomes would have been present in the second polar body?
Explanation / Answer
In which division meiosis did non disjuction occurs ?
Meiosis 1 , the chromosomes where the mother cell is passed .
In case of the trisomy 18 ,How many chromosmes would have been present in thefirst polar body ?
23 ,chromosomes ,consists of the 46 chromatids .
In case of trisomy 18 , how many chromosomes would have been present in the second polar body ?
24 chromosomes are present .
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