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  #1  
Old 08-20-2011
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DNA PCR amplification

PCR amplification is carried out on the region containing the CAG repeat, which of the following sets of primers would be used to amplify the CAG repeat in the brackets (CAG)
GAG TCC CTC AAG TCC TTC (CAG) CAA CAG CCG CCA CCG CCG
A. CTC AGG GAG TTC AGG AAG & CGG CGG TGG CGG CTG TTG
B. CTT CCT GAA CTC CCT GAG & CAA CAG CCG CCA CCG CCG
C. CTT CCT GAA CTC CCT GAG & CGG CGG TGG CCG CTG TTG
D. GAG TCC CTC AAG TCC TTC & CGG CGG TGG CGG CTG TTG
E. GAG TCC CTC AAG TCC TTC & GTT GTC GGC GGT GGC GGC

with Explanation plz how to answer such questions as i feel really confused .. thanks
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  #2  
Old 08-20-2011
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I think the answer is A
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Old 08-20-2011
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Quote:
Originally Posted by usluipek View Post
I think the answer is A
no unfortunately it isn't A
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  #4  
Old 08-20-2011
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Quote:
Originally Posted by usluipek View Post
I think the answer is A
the right answer is D
but i am not sure why ,, after long time i think that in PCR amplification one primer should be from 3'to 5' end while the other from 5' to 3' end
so if the sequence in DNA CAG so one primer should contain the sequence GTC while other should contain CTG .... i don't know if my way of thinking is right ... but it is written that the correct answer is D
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  #5  
Old 08-20-2011
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Correct Answer

The right answer is D
The Base pair given is
5' to 3'
GAG TCC CTC AAG TCC TTC (CAG) CAA CAG CCG CCA CCG CCG


the complementary base pairs to above strand will be
3' to 5'
CTC AGG GAG TTC AGG AAG [GTC] GTT GTC GGC GGT GGC CCG GGC

The DNA polymerase acts from 5'-3' Direction
Hence to polymerise CAG repeat the primer used must be complementary to
3' CTC AGG GAG TTC AGG AAG-5' i.e.
5' GAG TCC CTC AAG TCC TTC-3'

In the same manner the complementary base pair to
5' CGG CCG GGC GGT GGC GTC GTT 3
Will lead to CAG repeats hence this may be itself used as the Primer.
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  #6  
Old 08-21-2011
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Quote:
Originally Posted by usmle2011 View Post
The right answer is D
The Base pair given is
5' to 3'
GAG TCC CTC AAG TCC TTC (CAG) CAA CAG CCG CCA CCG CCG


the complementary base pairs to above strand will be
3' to 5'
CTC AGG GAG TTC AGG AAG [GTC] GTT GTC GGC GGT GGC CCG GGC

The DNA polymerase acts from 5'-3' Direction
Hence to polymerise CAG repeat the primer used must be complementary to
3' CTC AGG GAG TTC AGG AAG-5' i.e.
5' GAG TCC CTC AAG TCC TTC-3'

In the same manner the complementary base pair to
5' CGG CCG GGC GGT GGC GTC GTT 3
Will lead to CAG repeats hence this may be itself used as the Primer.
thanks soooooo much u really helped me
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