The Role Of Telomeres In Dna Replication Biology Essay

Telomeres are specialised protein constructions found on the terminal terminals of chromosomes in eucaryotes. Unlike procaryotic beings that have round DNA, eucaryotic beings contain additive DNA which is more likely to undergo onslaught, taking to the debasement of the DNA. Telomeres hence, play a important function in protecting the cells atomic DNA, by organizing a cap around the terminal terminals of chromosomes. Furthermore, telomeres carry out several other indispensable functions, some of which include ; keeping the stableness of chromosomes, enabling completion of DNA reproduction and besides cellular aging. All these functions are discussed in item through this text.

Briefly discuss all the functions of telomeres

Besides reference the telomeres are good in forestalling homologous recombination of chromosomes, as the broken terminals of Deoxyribonucleic acid are more prone to fall ining together.

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What are telomeres and their construction

Telomeres are composed of a protein nucleic acid composite which consists of two chief constituents ; telomeric DNA and proteins. The telomeric DNA is normally comprised of short tandem repetition units ( 6-8 bases ) , and G ( G ) rich bases that are grouped towards the terminal of the chromosome on the G-rich strand. This is the strand positioned 5 ‘ to 3 ‘ towards the terminal terminal of the chromosome ( Blackburn, 2001 ) . Typically in worlds and most other eucaryotic organisms the sequence of repetition units is normally AGGGTT. This sequence was proposed by Elizabeth H. Blackburn in 1991 through a series of experiments conducted in her early old ages of research ( Blackburn, 1991 ) . It was subsequently published by Jeremy M. Berg and his fellow authors in a book, corroborating the presence of this sequence in most eucaryotic beings ( Berg, 2012 ) . It is estimated that this repetition sequence is present in every telomere within human cells, hence, research workers have estimated that 0.02-0.06 % of the genome is telomeric Deoxyribonucleic acid by weight ( Blackburn, 2001 ) . Furthermore, the presence of this telomeric DNA sequence holds great importance towards DNA reproduction as it is responsible for the reproduction of the 5 ‘ terminal of the chromosome ; this mechanism of action is subsequently discussed.

The 2nd major constituent of telomeres, the proteins, besides play a critical function towards the operation of telomeres. Telomeres are unable to work efficaciously and expeditiously without the presence of a DNA protein composite which should be bound to the nucleotide sequence on telomeres. The binding of this DNA protein composite is merely possible when telomeric proteins recognise the nucleotide repetition units and bind to this successfully. This triggers the binding of other proteins present in the karyoplasm, doing the formation of a DNA protein composite ( Blackburn, 2001 ) .

Furthermore another indispensable protein nowadays in telomeres, is a specialised ribonucleoprotein enzyme known as telomerase. This enzyme is indispensable for the care of the telomeres and besides plays a cardinal function towards DNA reproduction of the cell ( Blackburn, 2001 ) . Telomerase is composed of a catalytic nucleus, comprising of a RNA fractional monetary unit and a catalytic protein fractional monetary unit. The RNA fractional monetary unit acts as a templet for the add-on of bases to the 3 ‘ terminal of chromosomes, during DNA reproduction. The protein fractional monetary unit catalyses this reaction ( Meyerson, 2000 ) .

The function of telomeres in DNA reproduction

As discussed antecedently, the major constituent of telomeres which plays a critical function in DNA reproduction is telomerase. This is a specialized ribonucleoprotein which contains its ain RNA templet, for the reproduction of telomere DNA. During DNA reproduction a primer attaches itself to the 5 ‘ terminal of a chromosome strand. Deoxyribonucleic acid polymerase so works to add bases from the 5 ‘ to 3 ‘ way on the sense strand. During this process, as the primer is attached to the 5 ‘ terminal of the chromosome, some familial stuff from this subdivision is non transcribed. Therefore the major function of telomeres during DNA reproduction is to guarantee that no familial stuff from the terminal terminals of chromosomes is lost, and as a consequence telomeres map to retroflex this un-transcribed part of DNA ( Blackburn, 2001 ) . Telomerase is a protein which assists this procedure through a reaction rhythm. Initially telomerase binds to the telomeric primer on the individual stranded Deoxyribonucleic acid. This primer is formed of course by the telomere as a consequence of the 3 ‘ overhang. Following this the first set of repetition bases are synthesised. Deoxynucleotide triphosphates are added to the repetition units on the telomere doing it to lengthen and the familial information to be replicated ( Wyatt et al, 2010 ) .

Telomeres and stableness

Telomeres are constructions which are indispensable in order to keep the stableness of chromosomes. Without the presence of telomeres, chromosomes are likely to undergo debasement and recombination with other chromosomes. This is non good to cells, for which ground the presence of telomeres is important to chromosomes. Research carried out by Wyatt in 2010 explains that earlier experimental processs display the presence of constructions known as telomere cringles in chromosomes. Today it is believed that, the major ground why telomeres hold importance in protecting the atomic Deoxyribonucleic acid from debasement or merger with other homologous chromosomes is due to the formation of these telomere-loops ( t-loop ) . T-loops are formed due to the presence of several nucleotide repetitions on a individual strand of DNA, doing a 3 ‘ overhang, which consequences in the G-rich strand being longer than expected. As a consequence the Deoxyribonucleic acid strand cringles, organizing the T-loop. Wyatt farther explains in his research that old experimental processs on human and mice telomeric DNA show similar tendencies about T-loops when the telomeres of both beings were viewed under an negatron microscope ( Wyatt, 2010 ) . Overall, most significantly the formation of the T-loop protects the cell and gives the chromosome stableness.

Furthermore, Wyatt and his fellow scientists besides explain that the ribonucleoprotein, telomerase is besides responsible for keeping the stableness of chromosomes. As mentioned antecedently the telomerase protein is composed of two fractional monetary units, one of which is the RNA fractional monetary unit. This is farther subdivided into two structural motives known as a box H/ACA sphere. This sphere is the component of the RNA fractional monetary unit which is responsible for the binding of proteins during the synthesis of telomeres and add-on of bases. Therefore this motive is an indispensable structural constituent of telomeres, which is important to the stableness of the telomere, as without the presence of these structural motives, the telomeres would be unstable and likely to debasement ( Wyatt, et Al, 2010 ) .

In comparing, research carried out by Deng and Chang in 2007 explains that telomerase is absent from bodily cells, for which ground after uninterrupted DNA reproduction, the telomeres shorten as a consequence of no bases being added to the telomeres via the ribonucleoprotein telomerase. Therefore as the age of an single additions, the rate of cell decease besides increases. This shortening of telomeres finally leads to their debasement change overing them into double stranded interruptions therefore taking to the instability of the chromosomes.

Telomeres and cellular aging

P53, towards the terminal, leads to senescence- as a consequence of telomere shortening, one time the length of the telomeres reaches a critical threshold, which is a degree where the length of the chromosome is excessively short to organize a telomere cringle and, therefore paly a protective function towards the atomic Deoxyribonucleic acid of the cell, the cell initiates a p53 and pRB-dependant DNA harm response. This takes topographic point in order to protect the cellular Deoxyribonucleic acid of the cell and hence the cell destroyed.

However, cells which have a faulty p53 and pRB pathway, lead to the formation of malignant neoplastic disease as, the cells continue to split through a series of cell divisions. This in bend consequences in tumour cell formation and hence malignant neoplastic disease.

Analysis of literature beginnings


The construction of telomeres is indispensable in enabling accurate and right map of telomeres. The presence of the tandem repetition units coupled with the presence of telomeric DNA proteins are indispensable in order for the telomere composite to map suitably.