The lagging strand is the strand of parent DNA that runs in the opposite direction that the replication fork opens. Because DNA polymerase adds nucleotides in  direction, RNA primers are added along the length of the newly single parent DNA strand to provide a  hydroxyl group onto which DNA polymerase adds nucleotides. DNA polymerase adds nucleotides to the RNA primer until encountering another primer. These segments of newly synthesized DNA are called Okazaki fragments. DNA polymerase I removes RNA primers and replaces them with DNA. Ligase seals the gaps between DNA, forming a continuous strand.

Telomeres are the regions at the ends of chromosomes that contain repetitive sequences of DNA. Telomeres are non-coding, and instead serve to protect the chromosome from deterioration and degradation. In DNA replication, there exists an “end replication problem”, which describes the inability to replicate the entire chromosome. The lagging strand cannot be copied in its entirety due to a lack of strand to attach another primer. Thus, the newly synthesized DNA molecule is shorter than the parent molecule. Because the telomeres are at the ends of chromosomes, telomere sequences are shortened with each consecutive round of DNA replication. However, telomerase solves this "end replication problem." It is a ribonucleoprotein, which means it contains RNA and protein to carry out its enzymatic function. It adds repetitive sequences to the ends of the DNA strand so that the chromosomes do not shorten over time.

Telomerase catalyzes the lengthening of chromosomes. Without telomerase, chromosomes would shorten with each round of replication, until the chromosome shortens, cutting into an important gene. At this time, the cell would not be able to carry out replication and/or make a gene product essential to its survival. If telomerase is overactive, cells' chromosomes would not naturally shorten over time, and they may continue to lengthen and divide uncontrollably (cancer).

DNA ligase joins the sugar-phosphate backbone of DNA strands through catalyzing the formation of phosphodiester bonds. The nicks in the backbone arise from Okazaki fragments and the action of topoisomerase.

There are three models of DNA replication: the dispersive model, the conservative model, and the semiconservative model. The dispersive model postulates that parental DNA cut into segments, each of which acts as a template for newly synthesized fragments. Together, DNA helices reassemble, containing daughter and parental DNA segments mixed together. The conservative model hypothesizes that the parental DNA double helix acts as a template for the daughter DNA molecule. This model results in one parental double helix and one daughter DNA molecule. The model that describes DNA replication is the semiconservative model. In this model, parental DNA strands separate and act as templates for daughter strands, resulting in two DNA molecules each with one parent and one daughter DNA strand. Thus, each newly synthesized DNA molecule has one parent strand bound to one daughter strand.

The origin of replication is the sequence of DNA where replication is initiated. The origin of replication often has a high content of adenine and thymine nucleotides because they are only bound together by two hydrogen bonds, making the helix easier to open and unwind. There are multiple origins of replication on each chromosome in eukaryotes, while there is only one origin of replication in prokaryotes. The origin of replication binds to initiator proteins that make up the pre-replication complex, which initiates replication.

The only false statement is that DNA replication of the lagging strand is continuous. The leading strand features continuous replication while the lagging stand is initially made up of discontinuous Okazaki fragments, which are sealed later by ligase.

There are four major types of mutations: deletions, duplications, inversions, and translocations. Deletions occurs when a chromosomal fragment is removed and not replaced. Duplications occur when a chromosomal fragment is aberrantly copied. Inversions occur when a chromosomal fragment reattaches to its original chromosome in reverse orientation. Translocations occur when a chromosomal fragment reattaches to a different part of the same chromosome, or a different chromosome altogether.

Helicase is the enzyme responsible for breaking the helix and unwinding the DNA into two separate strands. This allows the polymerase enzyme to attach and start adding base pairs for replication. Primase is responsible for setting and synthesizing RNA primers for polymerase attachment.

Acetylation of histones helps increase genetic expression. Acetylation is the process of adding an acetyl group. Methylation is used by the cell to differentiate between the two DNA strands of a newly synthesized DNA. Essentially, the highly methylated strand is the original or parent strand. This is integral in proofreading the new DNA.