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.

From the lab result, transcription and translation had just occurred in order to create the MHC molecules. In order for transcription and translation to occur, the DNA must not have been condensed (euchromatic).

Euchromatin is a term used to describe an area within the DNA that is much less condensed and highly active transcriptionally. Typically, these areas are seen in highly active cells that are producing many proteins. On the contrary, Heterochromatin are areas that are much more condensed and much less transcriptionally active. On electron micrograph images, euchromatin areas are typically lighter stained vs heterochromatin areas are much more densely stained.