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* genetics 9
 #136137  
  kashmala - 11/06/06 23:19
 
  A pregnant woman with a family history of fragile X
syndrome wants prenatal diagnosis of her fetus. Amplifica-
tion of the appropriate region of the FMRI gene by PCR is
attempted on DNA from amniotic fluid cells, but no ampli-
fied products are obtained. What is the best next step?
A Routine karyotype of the amniotic fluid cells
B Routine karyotype of the unaffected father
C Southern blot of the DNA from the anmiotic fluid
cells
D PCR analysis of the mother's FMR1 gene
E No further tests necessary
 
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* Re:genetics 9
#546789
  cd45 - 11/06/06 23:23
 
  e????  
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* Re:genetics 9
#546791
  rajesh - 11/06/06 23:24
 
  southern blot of the dna ie ,C  
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* Re:genetics 9
#546793
  rajesh - 11/06/06 23:24
 
  southern blot of the dna ie ,C  
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* Re:genetics 9
#546801
  neoplasia - 11/06/06 23:26
 
  EEEE  
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* Re:genetics 9
#546835
  step1_ca - 11/06/06 23:38
 
  ee  
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* Re:genetics 9
#546849
  kashmala - 11/06/06 23:46
 
  correct answer is C  
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* Re:genetics 9
#546856
  kashmala - 11/06/06 23:47
 
  C
Failure to find amplified product by PCR in such
a case could mean that the fetus is not affected or that
there is a full mutation that is too large to be picked up by
PCR. The next logical step is a Southern blot analysis of
genomic DNA from fetal cells. Routine karyotype of the
amniotic fluid cells is much less sensitive than a Southern
blot. Karyotype of the unaffected father cannot provide
information on the status of the FMR1 gene in the fetus,
because amplification of the trinucleotide occurs during oo-
genesis. For the same reason, PCR of mother's FMR1 gene
is of no value.
 
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* Re:genetics 9
#546912
  cd45 - 11/07/06 00:52
 
  nice q kash :))  
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* Re:genetics 9
#548206
  kashmala - 11/07/06 20:20
 
  thanks for appreciation :))  
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