Details about Cell Biology 3rd edition by Thomas D. Pollard
Cell Biology 3rd edition PDF free download by Thomas D. Pollard – Eukaryotic chromosomal DNA molecules are thousands of times longer than the diameter of the nucleus and therefore must be highly compacted throughout the cell cycle. This compaction is accomplished by combining the DNA with structural proteins to make chromatin. Chromatin folding must compact the DNA but still permit access of the transcriptional machinery to regions of the chromosome required for gene expression. The first level of folding involves coiling DNA around a protein core to yield a nucleosome. The string of nucleosomes, known as a 10-nm fiber, shortens DNA approximately sevenfold relative to naked DNA. In some specialized cell types this is further condensed into a 30-nm fiber that shortens the DNA six- to sevenfold more. However, it appears that in most cells the further folding of the 10-nm fiber involves coils and looping, and is remarkably irregular and dynamic.