Question

What is the difference between chromatin and chromosomes?

Answer 1

This is from a middle school science level:

Chromosomes are the things in the nucleus of a cell that carry genetic information. We're used to seeing them looking kind of like the letter X. You have two of each, one from Mom, the other from Dad.

Chromosomes are made of 2 chromatids. This is because you can only see them during the stage of the cell cycle called Mitosis, when the nucleus splits. At this stage, you need 2 copies of the genetic information, one to go into each new cell. So the cell has already copied the genetic information. The chromatids are joined together to form the X by a structure called a centromere.

The chromatids are made of a substance called chromatin. This is a single, very long strand of DNA. It is spiraled up a bunch of times to be small.

So, chromatin is a long strand of DNA, containing a bunch of genes. You have 23 pairs of these, 23 from each parent, for a total of 46. The chromatin is copied, so you now have 92 strands, that are each spiraled up to form the chromatids. The 2 copies of each chromatid are joined together by a centromere to form a chromosome. You have 23 pairs of these, for 46 total.