Question

We performed a final experiment where we determined the tightness of DNA packaging for this gene in wild-type toe cells, and in toe cells in which the Talon enhancer had been mutated as described for constructs g-k. In this experiment we isolated chromatin and determined if an enzyme cuts in the gene very well or very poorly, depending on how tightly packed the DNA is at the site of cutting.

c. Suggest why the ability of an enzyme to cut chromatin at a specific location might tell us about chromatin structure; specifically packing of DNA.

In this experiment, poor cutting gives a 7kb fragment of DNA, while fragments of 4kb and 3kb indicate good cutting of the DNA. The results are indicated below:

Construct                   DNA fragments observed    Chromatin structure

                                                                                    (tight, loose or intermediate)

g                                  4kb, 3kb

h and i                         7kb, 4kb, 3kb

j                                   7kb     

k                                  4kb, 3kb

d. Complete the table above to indicate the chromatin structure implied for each construct.

Answer 1

d-

Construct                   DNA fragments observed    Chromatin structure

                                                                                    (tight, loose or intermediate)

g                                  4kb, 3kb loose

h and i                         7kb, 4kb, 3kb Intermediate

j                                   7kb Tight

k                                  4kb, 3kb loose

c) The ability of an enzyme to cut chromatin at a specific location will tell us about chromatin structure; specifically packing of DNA.

The site of tightly packed DNA structure, makes it compacted in such away that it does not allow it to become easily available to the enzyme. while the site of loosely packed DNA, allow more space or easily binding of the enzymes to the DNA strands and makes more fragments of DNA.