is a term describes the dna–protein complexes that look like beads on a string

Histone

Explanation:

Histone describes the polypeptides rich in arginine and lysine, that are tightly associated with DNA in chromosomes in all eukaryotic cells.

They appear beads on a string and form the core of nucleosomes, around which DNA is wrapped. The 5 major histones are H1, H2A, H2B, H3 and H4

answer: - few nutrients

high pressure

low temperatures

explanation: 1. few nutrients:   open-ocean zone is located way far from the land, which is the main source of the essential nutrients.2. high pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.3. ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface. 4. varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.5. low temperatures:   the temperature of open-ocean zone ranges from a low of -2°c to an average of 17°c