In DNA replication the molecules of the DNA separates into two separate strands. Then complementary strands are produced they match up A-T & C-G. mRNA comes to the DNA and changes the DNA into RNA. The rRNA causes the proteins to form, then the tRNA matches the proteins (codons) and it's then known as an amino acid. I understand that mitosis is a part of cell division and the cell nucleus divides. Mitosis produces two genetically identical cells. Meiosis produces four different cells. None of the cells are the same. (Meiosis produces gametes).