Video

Animation 1

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in this animation we’ll see the
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remarkable way our DNA is tightly packed
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up so that six feet of this long
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molecule fits into the microscopic
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nucleus of every cell
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the process starts when DNA is wrapped
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around special protein molecules called
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histones the combined loop of DNA and
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protein is called a nucleosome
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next the nucleosomes are packaged into a
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thread the end result is a fiber known
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as chromatin
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this fiber is then looped and coiled yet
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again
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leading finally to the familiar shapes
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known as chromosomes which can be seen
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in the nucleus of dividing cells
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chromosomes are not always present they
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form around the time cells divide when
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the two copies of the cell’s DNA need to
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be separated
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using computer animation based on
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molecular research we are now able to
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see how DNA is actually copied in living
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cells you are looking at an assembly
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line of amazing miniature biochemical
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machines that are pulling apart the DNA
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double helix and cranking out a copy of
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each strand the DNA to be copied enters
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the production line from bottom-left
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the whirling blue molecular machine is
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called helicase it spins the DNA as fast
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as a jet engine as it unwinds the double
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helix into two strands one strand is
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copied continuously and can be seen
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spooling off to the right things are not
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so simple for the other strand because
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it must be copied backwards it is drawn
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out repeatedly in loops and copied one
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section at a time
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the end result is two new DNA molecules