Video Transcript
Which of the following statements
is true about chromatin? (A) Chromatin contains a high
amount of DNA and a low amount of protein. (B) Chromatin contains a low amount
of DNA and a high amount of protein. (C) Chromatin contains roughly the
same amount of DNA and protein. (D) Chromatin contains only DNA
molecules.
You’ll recall that eukaryotes, like
humans, are characterized by the presence of a membrane-bound nucleus to contain
their DNA. In humans, if you were to unpack
all the DNA inside a single nucleus, you would get about two meters worth of
DNA. This isn’t one long, continuous
piece of DNA. Instead, it’s organized into
structures called chromosomes.
In humans, there’s 23 pairs of
chromosomes, or 46 in total. Here’s what one of these
chromosomes might look like. Each chromosome is a highly
packaged molecule of DNA that’s coiled up and wrapped around special proteins called
histones. Because of this extensive packing,
a lot of DNA can fit inside a single cell. Nearly 150 base pairs of DNA can
wrap around a histone complex of eight histone proteins. This forms a structure called a
nucleosome. Nucleosomes coil up tightly to form
chromatin, which wraps up further to form the chromosome. Chromatin contains about the same
amount of protein, mostly in the form of histones, as DNA.
Therefore, going back to our
question, the statement that is true regarding chromatin is given by answer choice
(C). Chromatin contains roughly the same
amount of DNA and protein.
