Video Transcript
Which of the following is true
about histones that bind with DNA? (A) They have a high content of
leucine and alanine. (B) They have a high content of
acidic amino acids. (C) They are loosely bound with
DNA. (D) They are positively
charged.
You’ll recall that our DNA is
located within the nucleus of our cells. There’s a lot of DNA stuffed inside
this nucleus. In fact, if you were to take out
the DNA from a single cell and stretch it out, it would be about two meters in
length. All of this DNA isn’t one long,
continuous molecule of DNA. Instead, it’s organized into
structures called chromosomes. In humans, we have 23 pairs, or 46
chromosomes, in total. Let’s take a closer look at one of
these chromosomes.
DNA is wrapped up tightly around
special proteins called histones. Histones carry a positive charge,
which is what allows it to bind tightly to the negatively charged molecule of
DNA. DNA wraps around a group of eight
histone proteins to form a structure that we call a nucleosome. Nucleosomes are further coiled and
compacted to form chromatin, which compacts further into the chromosome structure we
see above. This is how so much DNA can be
stuffed inside a single cell.
Going back to the question, the
statement that is true regarding histones binding DNA is given by answer choice
(D). They are positively charged.
