Telomerase
Telomerase is a specialised ribonucleoprotein reverse transcriptase enzyme[1]. It carries its own RNA molecule. Telomerase is functional at the tips of chromosomes in areas known as telomeres. The main function of telomerase is to extend the 3' ends of DNA strands by adding 'TTAGGG' repeat sequences as it is not possible for DNA polymerase to replicate 3' ends. Elizabeth Blackburn (molecular biologist, co-discoverer of telomerase and co-winner of the 2009 Nobel Prize for Physiology or Medicine) compared telomeres to the tips of the shoelaces which help to prevent fraying[2]. Telomeres function to protect DNA from molecular attack as well as preventing strands of genetic material from 'sticking' to the DNA strand[3]. Telomerase is
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Telomerase is a unique enzyme as in addition to having DNA polymerase activity, it also contains an RNA sequence template which is complementarity to the repeating telomeric sequence. It consists of various RNA subunits including TP1, TP2 and TERT. TERT is a catalytic subunit that is homologous to reverse transcriptase. Its 'fingers' and thumb' pull the telomerase RNA and telomere DNA strands to the active site- the 'palm' where the telomere is elongated[4]. Unlike other polymerases, TERT also includes an amino-terminous which binds telomerase …show more content…
They showed that the ends of chromosomes are protected by telomeres and telomerase. Jack Szostak studied yeast cells and saw that their linear chromosomes were rapidly degraded. Coupled Blankburn's study of telomeres in Tetrahymena, they decided to couple yeast minichromosomes and Tetrahymena telomeres to see if the telomeres could prevent chromosome degreadation. The experimental outline is shown below in Figure 4. They proved their hypothesis and showed that telomeres and telomerase are capable of protecting
The study also found that an increase in γ-H2AX (a marker for DNA double-strand breaks) and a decrease in RAD1 (a marker of HR directed DNA repair) focus-positive cells was associated with a depletion of MEN1 expression as predicted. The study also predicted that NHEJ could function to repair double strand breaks, and would increase with a loss of MEN1 functionality. The study found this prediction to be true. The study also investigated the role of ATM and ATR DNA damage kinases in relation to MEN1, and found that MEN1 is protected from ubiquitin mediated degradation through phosphorylation by ATM and ATR protein kinases. One of the most significant results from this study involved determining the functional relationship between the expression of HR target genes and MEN1, as well as investigating the mechanism of action involved in the cellular process.
(pg. 204) The protective telomere have raised the question, is a genome immortal? It does seem possible that it could be immortal but in reality there really is no
In this course, we have studied the many characteristics of DNA which include that it is double helix that contains genetic material and it is kept stable by hydrogen bonds. DNA is made up of smaller units called nucleotides. In turn, each nucleotide consists of a phosphate group, a sugar and a nitrogenous base. DNA also include base pairing which is the 'copying' mechanism for DNA. In DNA, bases are the adenine base, which only pairs with a thymine
Elizabeth Blackburn The work of Elizabeth Blackburn concerns the performance and production of telomeres, which are the ends of eukaryotic chromosomes. Telomerase specifies the sequence of telomeric DNA by using a short sequence of the telomerase RNA moiety as the guide for DNA synthesis. Therefore, telomeric DNA is a vital chromosomal component which is unusual as it is made by copying an RNA sequence; which is an extremely specialised, distinctive mechanism.
Genetic mutations occurring in any of these three telomerase genes- TERT, TER, or dyskerin; or telomerase-associated proteins can result in compromised activity of telomerase resulting in low levels of telomerase and insufficient telomere maintenance. This can manifest in one of a number of telomere syndromes such as idiopathic pulmonary fibrosis (IPF) and dyskeratosis congenita (DC) (Tomlinson et
The selected paper is purposed by Roger A. Browse and Scott A. Little titled “The Effectiveness of Real-Time Graphic Simulation in Telerobotics”. The objective of the experiment is to test the effectiveness and performance of the real time graphic simulation in teleoperational robotic systems (telerobots) by having perspective control of simulation. Effectiveness of the telerobotics also has been compared by using different display methods. The method used in this experiment was displayed an animation sequence of the robot moving the gripper toward a block placed in the scene. Collision between the gripper and the block were predicted.
A group of 3 nucleotides is called codons. Each codon on the mRNA molecule matches a corresponding anti-codon on the base of a tRNA molecule. The tRNA anti-codon attaches to the mRNA codon. Then, the larger subunit of the ribosome disconnects an amino acid from a corresponding tRNA molecule and adds it to the growing protein chain. When the mRNA is completely decoded a protein is made
Primase: Synthesises a single RNA primer at the 5’ of the strand. Ligase: It joins Okazaki fragments by phosphodiester bonds. An enzyme called helicase unwinds the double-stranded DNA .Several
For growth and development, every cell requires its full fledging machinery to duplicate, so for DNA as well. For initiation of replication requires energy and enzymes. DNA is double stranded helix which requires linear conformation for replication. So to help it out special enzymes and proteins bind to it. Topoisomerase cuts the DNA strand and made path for helicase to bind to DNA strand.
Nucleotide excision repair is an important DNA repair system that corrects UV induced genetic damages. One example of such damage is the formation of a covalent bond between two adjacent thymine bases on a DNA strand (thymine dimers). This causes a bulk in the DNA strand and disrupts DNA replication. The process includes the proteins UvrA, UvrB and UvrD as well as DNA polymerase and DNA ligase.
They are composed of a long double stranded (kilobases). The double strand telomere sequence are linked to specific place on the DNA (telomeric repeat binding factor 1- TRF1, and telomeric repeat binding factor 2 – TRF2). The TRF2 is very important for protection and the loop conformation.
Telomere and telomerase: A telomere is a repeating DNA sequence (for example, TTAGGG) at the end of the body's chromosomes. The telomere can reach a length of 15,000 base pairs. Telomeres function by preventing chromosomes from losing base pair sequences at their ends. They also stop chromosomes from fusing to each other.
It has three layers that are composed of the fibrillar center (FC), the dense fibrillar component (DFC) and the granular component (GC). The nucleolus is a non-membrane bound organelle and found in the nucleoplasm. Though it lacks a membrane, one cannot assume that the diffusion rate to each layer is equal. Its function is to transcribe rDNA, remove introns from pre-rRNA and modify an rRNA with the assistance of ribosomal proteins. The modifications made on the rRNA are executed by small nuclear ribonucleoprotein (snRNP) complexes which consist of small nucleolar RNAs (snoRNAs) and nucleolar proteins.
Introduction Telomeres are the ends of chromosomes that consist of tandem repeats of DNA sequences, with the length varying in various species. (Wong et al., 2008). The specific role of telomeres is to protect and guard the chromosomal ends from being damaged, and so if they become too short they lose their protective nature and leave the chromosomal ends exposed to damage (Wong et al. 2008). Types of damage that can be done to telomeres include degradation, recombination, as well as activities that repair DNA and may shorten the telomeres (Samper et al., 2001). The enzyme telomerase lengthens chromosome ends and restores length of the telomeres (Marion et al., 2009).