Which of the following common items would best represent the primary structure of a protein

The answer is; Beads of different color joined together on a piece of string

Primary structure of a protein is right after it has been translated from an mRNA by a ribosome. It is linear and has not yet been folded into a functional protein. The beads in the item represent amino acids joined together by peptide bonds.  

as in mitosis, dna replication occurs during interphase.   in meiosis, it occurs specifically in s phase of interphase 1.