How DNA is Packaged (Advanced)


In this animation we’ll see the
remarkable way our DNA is tightly packed up to fit into the nucleus of every cell. The process starts with assembly of a
nucleosome which is formed when eight separate histone proteins sub
units attach to the DNA molecule. The combined tight loop of DNA
and protein is the nucleosome. Multiple nucleosomes are coiled together
and these then stack on top of each other. The end result is a fiber of packed
nucleosomes known as a chromatin. This fiber, which at this point is condensed
to a thickness of thirty nanometers, is then looped and further packaged using
other proteins which are not shown here. This remarkable multiple folding allows
six feet of DNA to fit into the nucleus of each cell in our body. An object so small that ten thousand
nuclei could fit on the tip of a needle. The end result is that the DNA is
tightly packed into the familiar structures we can see through
a microscope, chromosomes. It is important to realize that
chromosomes are not always present. They form only when cells are dividing. At other times as we can see here at
the end of cell division, our DNA becomes less highly organized.

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