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ans plz anyone...nbme - samg
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06-03-2006, 10:40 AM
1. Which of the following techniques is most accurate in showing that two bacterial DNAs are identical?
A. Hybridization B. Northern blotting C. Nucleotide sequencing D. Polymerase chain reaction E. Restriction enzyme analysis
06-03-2006, 12:14 PM
B is for mRNA so used to see if there are same functional genes are expressed by both bacteria but doesnot tell you anything about other nonexpressive elements like promoters ,spacer DNA ,......... that may be different between the two DNA molecules
About C it should be the most accurate method but if u think about it it is very expensive first and second it is time consuming may be years and as u know they are still sequncing Human genome scince 1990 till these dayes so it isnot reasonable to use it for our experiment but u can use it for sequncing short segments of the DNA About D it is used for amplification of certain segments or genes but not amplification the whole DNA molecule and if u think little about it this technique will not tell u anything about the exact squence of bases in the DNA molecules so it is useless About E even the two molecules give u the same band paterenes on the gel but again it will not tell you nothing about the base sequences in the DNA molecules so the DNA molecules may share many restriction sites but different squences so it isnot dependable so after all this i think the best choice is A although it has one disadvantage that some times when probes are used for hybridization even there is different in few bases between the two molecules the probes will still able to attach to their complemetary sites and will miss some little difference in squence but it is still the best choice
06-03-2006, 12:44 PM
ok if u chose this technique C so if u are bacterologist and working on some bacteria and wanna to prove if their DNA is identical and ask u "excuse me sir when will u tell us if they are identical or not" and u say "um may be after 5 or 6 years so i will tell u ok it is a great experiment but i may be dead at that time."
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