Molec. Bio help (needed)

pickett at kenyon.edu pickett at kenyon.edu
Mon Mar 1 21:49:25 EST 1993


Hello my name is John C. (Pickett at kenyon.edu) and I have four questions which I
need answers to. If anyone has the time to answer them would you please send 
them to me?  I need answers as soon as possible (March 3....spring break starts
the 5th).  If you can only answer one or two that's fine just send me what you 
know.  Thanks alot.

Here they are:

1)The view that DNA polymerase moves progressively along the template DNA as it
adds one nucleotide after another to the growing chain was initially intuitive. 
You want to study whether DNA polymerase indeed exhibits processivity in its
replication of templates in vitro.  You have available to you two synthetic
DNA's one of which is composed entirely of A's on one strand and T's on the
other and another with C's on one strand and G's on the other.  Also, you have
your choice of raioactively labelled DNA precursors (alpha-^32P-dNTP's). 
Finally, you have bacterial extracts containing the necessary machinery
(including polymerase) to replicate DNA.  Devise and describe an experiment to
test whether DNA polymerase acts processively, i.e. does not dissociate from
template DNA as a new DNA strand is synthesized.  Be sure to be clear about
experimental procedures, about hypotheses being tested, and about expected
results.  We know of course that bacterial DNA polymerase does act
processively.  What features of the Klenow fragment of DNA Polymerase I
facilitate this type of action?

2)How was it concluded that the sugar-phosphate backbones of DNA were
antiparallel?

3)X-ray diffraction analysis data suggested helicity in the DNA structure.  
How was it concluded that the structure of DNA was a double helix?

4)Why are purine-purine and pyrimidine-pyrimidine pairs improbable?


Once again thanks for any help which is provided.

John.
Pickett at kenyon.edu



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