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Old 12-19-2011
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DNA Mechanism of Mosaic Turner Genotype

18 yr old female with primary amenorrhea and a swelling in the neck area is analyzed to have some cells containing 46XY and others 45X. What is the mechanism of this finding?

A. non disjunction in meiosis
B. Robertsonian translocation
c. reverse tranlocation
d. Skewed X inactivation

Post answer with explanation
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Old 12-19-2011
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Are the options correct?

It has to be non-dysjunction in mitosis not meiosis!
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Old 12-19-2011
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Sorry, yeah it is Non dysjunction in mitosis. Correct ans is A.
I cannot understand how in non disjunction half of the cells will have XO and half have XY. I thought that can happen only in skewed X inactivation which is normal in females.

Doxo can u explain?
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ok yeah i got it
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Old 12-20-2011
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Non dysjunction in mitosis. Correct ans is A.

i just memorize it in step 2 i dont know y?when iwill read gentics iwill know
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nondysjunction in mitosis means mosacism
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Old 12-20-2011
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it should be non dysjunction in mitosis. had it been in meiosis, mosaciasm wudnot have been occured, all cells would be XO.
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Correct Answer the answer is A,there certain important concepts

first of all Turners syndrome is on account of complete or partial monosomy of X chromosome, characterized primarily by hypogonadism in phenotypic females.
now coming to monosomy, for that have to know whats aneuploid cell
a normal cell must acquire chromosome complement in exact multiple of the haploid number (23), if it does not occur in exact multiple its called aneuploid,the mechanism behind aneuploid is non-disjunction and anaphase lag, non-disjunction accounts for 2n+1,trisomy or 2n-1, thats monosomy. So as mentioned earlier turner syndrome involves monosomy, hence the answer is non-disjunction
advice to gain concept of mitosis and meiosis for better understanding
check out this video
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