Dna replication: dna contains two separate strands, strands are complementary to one another, serve as templates, controlled by dna polymerases, they check whatever they make. Double strands: nucleotides need to match up they are complementary. It is always described as a chain but in fact, this is not how it looks. It is extremely wrapped up and coiled and squeezed into the nucleus of the cells, lots of dna in there. If you have dna completely wrapped up, it cannot be transcribed. It must be loose so polymerases can actually attach and start working on it. On the chromosome during interphase of mitosis you suddenly get loosening of the complex structure. This is when the strands loosen and open up to be transcribed. This means that the packaging determines when dna can be transcribed. Packaging is equally as important to the regulatory factors.