Video Transcript
Each chromosome is made up of DNA tightly coiled around proteins many times. What is the name of these proteins?
One of the defining features of eukaryotes, like humans, is the presence of
membrane-bound organelles, including the nucleus to contain our DNA. We have a lot of DNA packed into a nucleus. In fact, if you were to take out all the DNA from a single human cell and stretch it
out, it would be about two meters in length. This isn’t one long, continuous molecule of DNA; instead, it’s organized into
structures called chromosomes. In humans, we have 23 pairs of chromosomes, or 46 in total.
Let’s take a closer look at one of these chromosomes so we can answer this
question. Here we can see that the DNA is wrapped up very tightly around special proteins
called histones. Around 150 base pairs of DNA can coil around a group of eight histone proteins to
form a structure called a nucleosome. And these nucleosomes can coil up tightly to form chromatin. The chromatin itself can wrap up further to form the chromosome structure. This tight packaging is how so much DNA can fit inside a single nucleus.
Going back to our question, the proteins that DNA is tightly coiled around are called
histones.
