The role of the topoisomerase enzyme is to unwind the DNA, allowing enzymes such as DNA helicase access to the nucleotide sequence. DNA helicase is responsible for breaking the hydrogen bonds responsible for holding double-stranded DNA together. This creates the replication fork and allows DNA polymerase access to the nitrogenous base sequence. The role of DNA polymerase is to place nucleotides once the DNA has been unwound, synthesizing the daughter DNA strands. DNA ligase binds nucleotide fragments together during synthesis. Telomerase is responsible for lengthening the telomeres at the ends of chromosomes.

Okazaki fragments are found on the lagging strand during replication. Because these fragments will not be attached together following strand synthesis, a protein is required to combine the fragments. DNA ligase will follow DNA polymerase on the lagging strand, and combine the fragments in order to create a complete strand.

DNA polymerase is responsible for recruiting and joining nucleotides in the 3'-to-5' direction, but cannot fuse Okazaki fragments on the lagging strand. Primase lays down an RNA primer to recruit DNA polymerase prior to replication. Helicase unwinds the DNA helix in order to expose the template strands. RNA polymerase is involved in transcription, and plays no active role in DNA replication.

Frameshift mutations involve the insertion or deletion of a nucleotide in a DNA sequence, changing the reading frame of the entire nucleotide sequence after the mutation. As a result, every subsequent codon is also affected, creating a change in the organism's phenotype.

Oftentimes, this results in a premature stop codon, which causes the protein product to be shorter than an unaffected polypeptide.

DNA polymerase always reads DNA strands in the 3'-to-5' direction, creating a complimentary 5'-to-3' strand. As a result, the parent strand oriented in the 3'-to-5' can be replicated seamlessly, but the strand that is unraveled in the 5'-to-3' direction will require multiple attachment points for DNA polymerase so that the whole strand can be replicated in the reverse direction.

These multiple segments of replication are called Okazaki fragments, and can only be found on the lagging strand, which is replicated more slowly.

Cohesin is a protein that is not involved in DNA replication. It has diverse functions, including regulating sister chromatids during mitosis.

During replication, helicase is responsible for unwinding DNA strands to expose the site for replication. DNA polymerase III functions primarily to add new nucleotides, while DNA polymerase II proofreads and corrects errors in replication. DNA ligase is responsible for joining breaks in the DNA backbone.

DNA polymerase III is the enzyme that attaches to the RNA primer and adds DNA nucleotides complementary to the template strand in order to create the new, growing strand.

Primase is responsible for synthesizing the RNA primer. Helicase unwinds the DNA and creates the replication fork for other enzymes to bind. Ligase repairs breaks in the sugar-phosphate backbone and binds Okazaki fragments together. DNA polymerase I has a number of functions, including replacing the RNA primer with DNA nucleotides.

Helicase, gyrase, and DNA polymerase are all used in the process of DNA replication, which takes place in the nucleus. Helicase is responsible for "unzipping" DNA, separating its two strands and unwinding the double-helix. Gyrase is responsible for relaxing the DNA strands and relieving tensions during unwinding. DNA polymerase synthesizes the the new DNA strands by recruiting nitrogenous bases.

The polarity of nucleic acids, and therefore DNA molecules, describes the chemical orientation of the macromolecule. Each nucleotide has a  end, which refers to the fifth carbon of the deoxyribose sugar ring that has a phosphate group attached to it, and a  end, which is the third carbon in the sugar ring that has a hydroxyl group attached to it. DNA polymerase can only add nucleotides to the  hydroxyl group of a nucleotide. This results in a new DNA strand elongating in the  to  direction.

In the initiation stage of DNA replication, a number of enzymes are involved. These include the initiator proteins in the pre-replication complex, DNA helicase, single stranded binding proteins, and topoisomerase. Topoisomerase is an enzyme that helps relieve winding and unwinding tension in DNA that arise from the helical structure of the DNA molecule. The DNA ahead of the replication fork often becomes tangled and/or supercoiled. Topoisomerase cuts the DNA to relieve the stress and allow the DNA to relax by unwinding a few times.Later during the replication process, the DNA rewinds and these breaks are resealed.

In the process of DNA replication, DNA polymerase can only add nucleotides to an already existing DNA strand. To overcome this difficulty in synthesizing new DNA strands, the cell utilizes RNA primers. RNA primers are short strands of RNA synthesized by the enzyme primase. Primase is a type of RNA polymerase that does not need a free  hydroxyl as a substrate, like DNA polymerase. Thus, it can lay down RNA nucleotides using the DNA parent strands as templates to provide DNA polymerase with the substrate it needs to begin elongation. RNA primers are also used in lagging strand synthesis, since DNA polymerase can only add nucleotides to the  end of a nucleotide. Thus all nucleic acid polymerization occurs in the  direction. DNA polymerase I removes the RNA primers, replacing them with DNA, then DNA ligase seals the gaps between DNA on the lagging strand.