The nucleotide is the single unit of DNA comprising the sugar molecule (deoxyribose) which is bonded to the base (A/T/C/G) (this combo is the nucleoside),plus the phosphate group (which bonds the C3 carbon atom of one sugar molecule to the C5 carbon molecule of the next one along in a phospodiester bond).

The string of nucleotides comprises a single strand of DNA.

A chromatid (which consists of chromatin – which is DNA plus its associated proteins, including histone) is one of the two ‘rods’ or ‘arms’ of the typical X shaped chromosome that we see at mitosis (when the DNA is highly condensed into its typical X shape). The two chromatids in a chromosome are clamped together (ie, the fulcrum of the X) at the centromere.

So:

Nucleoside = sugar + base
Nucleotide = sugar + base + phosphate
Single strand of DNA = sequence of nucleotides

Chromatin = DNA (double strand forming the double helix) plus proteins (scaffold for the DNA)
Chromatid + one half of a condensed chromosome

It IS confusing, but I hope that clarifies a bit (and I hope others will confirm I’ve got it right!!!!!)

Regards, Julie

Glad to have helped – but I’d definitely feel more comfortable if one of the experts here either confirmed or corrected my answer. I’m much more comfortable asking the questions than attempting the answers!

I think I’m right on this one though, but as I say, I would await confirmation or correction by one of the team of helpful resident experts here!! 🙂
Regards
Julie