Essay on Telomeres: Implications and Current Research

Instead of losing telomeres after each reproduction, the cells replenish, or lengthen, the telomeres using an enzyme called telomerase.

The length of the telomere indicates age-related diseases, unhealthy lifestyle, and longevity in the lifespan.

In Chapter 27 “The Secret to Immortality” of The Immortal Life of Henrietta Lacks Rebecca Skloot provided an explanation to why HeLa cells were “immortal” unlike other mortal cancer cells; the p53 tumor suppressor gene had been “turned off” by the Human Papilloma Virus Lacks had. She mentions how according to the Hayflick Limit, human cell’s were able to replicate an average of fifty times. In addition, she explains how telomeres in cells shrink slightly every time the cell divides. According to Aging Cell’s 2004 article “The Cellular Lifespan and Senescence Signalring in Embryonic Stem Cells,” tumor cells “have high telomerase activity” yet they are not immortal. HeLa cells, similarly to Embryonic Stem (ES) Cells have the tumor suppressor gene p53 turned off. This differentiates HeLa from other tumor cells; while other tumor cells will replicated more than the average cell and eventually reach senescence, HeLa continues to replicate to this day thanks to the HPV virus that turned off its

Telomerase is able to add DNA nucleotides to the ends of telomeres (the end of DNA sequences). After replication, a small amount of the telomeres are cut off. When the telomeres are cut too many times, the cell has met its Hayflick limit. It is believed that when an individuals cells have divided too many times, that they die.

As our cells divide and our DNA replicates, our telomeres provide a start and an end point for the enzyme DNA polymerase to attach to our chromosomes and replicate our DNA. By using a repeated, non-coding section of DNA as the starting point for this replication, the telomeres allow our cells to replicate without damaging important genes at the attachment point of the replicating enzyme. As this occurs though, our telomere begin to lose base pairs

After recognizing the restriction sites, the restriction enzymes cut off the DNA strands at these points, leaving sticky ends on the original DNA fragment. The restriction enzymes can also travel to other cells to cut off DNA sequences, the sequences that can match the bases of the original sequence. The sticky end will find other sticky end to form a new recombined DNA sequence, obeying the law of base-pairing.

Repeat instability is mediated by DNA replication, repair, recombination and transcription in specific tissues and stages of development and cell growth.

Deoxyribonucleic acid, or in its’ simple form DNA, contains the code for all characteristics of an organism which is completed by a double helix structure. The structure is made up of a back bone and the four gene groups which include thymine, adenine, cytosine and guanine. The double helix structure contributes to the cell division process

The genome is the complete set of an individual’s inheritable traits or it’s DNA. As a fetus develops, signals are received that cause incremental change in the gene expression patterns. The DNA in our bodies is wrapped around proteins called histone. The histone and DNA are covered in chemical tags. This structure is called an epigenome. The epigenome shapes the structure of the genome. Epigenetic marks are modifications of DNA and histones. The epigenome tightly wraps inactive genes and allows active genes to be more easily accessible. The epigenome adjusts specific genes in response to our changing environment. The programming of neurons through epigenetic mechanisms is critical in neural development. A type of cellular memory is formed when those changes occur. These are epigenetic tags. Each tag records the cell’s experiences on the DNA. This is to help stabilize gene expression. Over time, and with thousands of different experiences, an epigenetic profile forms for each cell type. Each one is unique, with a distinct identity and a specialized function. A flexible epigenome allows us to adjust and learn from our mistakes. The epigenome responds to signals. These signals come from a variety of places. From fetal development to old age, our epigenome is effected by our environmental factors.

On September 12, 1016, Belmont University graciously allowed Dr. Katherine Friedman from Vanderbilt University to come and talk to a crowd of students about the tendencies of how deoxyribose double stranded breaks can during cell replication and the elements required to hopefully repair this ordeal. She began the session by discussing what chromosomes are composed of and how they are produced, accompanied by visual and statistical representations. Moving on, she touched on how double strand breaks are a huge threat to a cell's, an organisms, stability. Correspondingly, she described what can cause these breaks; chemical factors, as well as inner cell disruptions during replication that are sometimes hard to remedy. However, she also stated that this breaks can occur on purpose, mostly in the immune system in efforts to make antibodies.

Telomerase (or terminal transferase) is an enzyme made of proteins, specifically reverse transcriptase (Telomerase Reverse Transcriptase-TERT), and RNA subunits. Nonetheless, chicken TERT (chTERT) shares 45% amino acid identity with human TERT (hTERT). However, chTERT is larger than the hTERT because of an extensive N-terminal flexible linker region. Also, chTERT is found on chromosome 2q21 near an interstitial telomere site. Generally, the role of this enzyme is to elongate the end of chromosomes by adding the repeated base sequence of TTAGGG, as described above. This enzyme can be found in fetal tissue, germ cells, and tumor cells. Telomerase activity is critical high on development because of the continued growth and division of the cells.

# Explain the process by which DNA is able to make copies of itself also including an explanation of why it is considered semiconservative replication - There are four steps to replication

Elizabeth Blackburn is an amazing woman; who comes from a family of physicians. She has always had a passion for animals and science; she found biology to be her favorite subject in school. She was fascinated by the visual impacts of science through books. Perhaps, it is her enthusiasm for biology that inspired her to be one of the leading biochemists today. Elizabeth helped in the discovery of “the fountain of youth.” Elizabeth and two of her colleagues discovered a way for chromosomes to be copied during cell division. Within this discovery, they also found a unique DNA sequence in the telomeres that protects these cells against degradation. In 2009, Dr. Blackburn was awarded the Nobel Prize in Medicine.

There have been studies on the limit of how many times a cell can divide, and it was later shown that telomere shortening was just slowly counting down to the deterioration of the cell (Okereke, Prescott, & Wong, 2012).

All living organisms, from amoebas to humans, have a molecular code called DNA in their cells, which instruct the activities that keep the organism alive. DNA is made up of long, twisted strands of four molecular “letters” (A, T, G, and C), which pair up according to their complementary base pairs, and their order determines how proteins — the vital molecules that perform all the major tasks in our cells — are made. (Refer to Diagram 1 to help sum up the concept.)