The level of dna packaging brought about by the formation of looks like beads on a string. 1400-nm chromatin fibers nucleosomes scaffolds 2-nm chromatin fibers 30-nm chromatin fibers

Answer: nucleosomes

Nucleosomes are one vital structures found in eukaryotic DNA. They enables the compact packaging of the genetic material into chromosomes. It is composed of a DNA sequence wrapped around the core of a protein type called histone. These are highly alkaline and act as spools around which DNA winds. They are also known to be involved in gene regulation.  

the element that provides strength to the exoskeletons of clams and oysters is phosphorus. this is so because calcium carbonate is the main component in the shells.

explanation: