Genomic DNA from the nematode worm Caenorhabditis elegans is organized by nucleosomes in the manner typical of eukaryotic genomes, with 145 bp encircling each nucleosome and approximately 55 bp in linker DNA. When C. elegans chromatin is carefully isolated, stripped of nonhistone proteins, and placed in an appropriate buffer, the chromatin decondenses to the 10-nm fiber structure. Suppose researchers mix a sample of 10-nm-fiber chromatin with a large amount of the enzyme DNaseI that randomly cleaves DNA in regions that are not protected by bound protein. Next, they remove the nucleosomes, separate the DNA fragments by gel electrophoresis, and stain all the DNA fragments in the gel.
a. Approximately what range of DNA fragment sizes do you expect to see in the stained electrophoresis gel? How many bands will be visible on the gel?b. Explain the origin of DNA fragments seen in the gel.

In view of the fact that we are firstly taking away the proteins that are non histone, only the DNA connected with histone proteins will be protected from the action of DNase I. 145 bp of DNA is attached with histone proteins and every nucleosome is attached with each other through a linker DNA.

DNase I might cut at any portion of 55 bp linker DNA. So, it is projected to see fragments of 145bp to 200 bp nucleotides in the gel.

However, given that the difference among the bands won't be important we will see a single band in the 145-200 bp region.