DNA Structure and Replication

ID #1111

I have a question about chromatin structure. In our lecture notes, I have written that the enzyme, nuclease, digests the linker DNA that is between the "beads." So does the linker DNA move to another location? Or does it stay there? I am just confused on where the linker DNA goes and what is the function of it if it ultimately is just digested.

The most important thing to realize here is that this nuclease digestion was part of an experiment done in a laboratory. This is NOT something a cell would normally want to do! It's one thing, as we noted in class, to "nick" a strand of DNA to do supercoiling -- the DNA gets put back together correctly. Random nuclease digestion would most likely be catastrophic to a cell. But in a test tube during an experiment, the linker DNA gets "chopped up" (degraded) into individual nucleotides, which then just hang out in the tube until the end of the experiment -- they don't "do" anything.

Now if you've been following along with some of our recurring themes in MCB 150 (and biology in general), you might be wondering if nucleases are naturally-occurring enzymes, or if we've constructed them only for experimental purposes. Because on the surface, knowing that cells don't make what they don't need AND they aren't likely to make molecules so hazardous to their own survival, you might guess nucleases are laboratory creations. But they're not. Under specifically controlled (and appropriately sequestered) conditions, cells have a need to degrade nucleic acid -- just not chromosomal DNA in a functional nucleus!! We'll visit a few of those instances throughout the semester.

Print this record Print this record
Send to a friend Send to a friend
Show this as PDF file Show this as PDF file
Export as XML-File Export as XML-File