Where Does the Phosphodiester Bond Connect the Two Nucleotides?

Bedroc of DNA Replication

DNA replication uses a semi-conservative method that results in a double-unaccompanied Desoxyribonucleic acid with cardinal parental filament and a new-sprung daughter maroon.

Learning Objectives

Explain how the Meselson and Stahl experiment conclusively established that DNA replication is semi-conservative.

Key Takeaways

Key Points

• In that respect were threesome models suggested for DNA reverberation: conservative, semi-moderate, and dispersive.
• The conservative method acting of replication suggests that parental DNA remains together and newly-lance-shaped daughter strands are also together.
• The semi-conservative method of replication suggests that the two parental DNA strands attend to as a template for new DNA and after replica, all double-unaccompanied Deoxyribonucleic acid contains one strand from the parental Deoxyribonucleic acid and one new (daughter) strand.
• The dispersive method acting of replication suggests that, after comeback, the two daughter DNAs have alternating segments of both maternal and newly-synthesized DNA interspersed on both strands.
• Meselson and Stahl, using E. coli DNA made with two nitrogen istopes (¹⁴N and ¹⁵N) and density slope centrifugation, discovered that DNA replicated via the semi-conservative method acting of replication.

Key Terms

• DNA replication: a biological process occuring in all support organisms that is the footing for biological hereditary pattern
• isotope: any of two or more forms of an component where the atoms have the same numerate of protons, but a different number of neutrons within their nuclei

Fundamentals of DNA Replication

Watson and Crick's discovery that DNA was a two-marooned double helix provided a suggestion every bit to how DNA is replicated. During cellular phone segmentation, each DNA speck has to be perfectly copied to ensure very DNA molecules to move to each of the two daughter cells. The double-stranded social structure of DNA advisable that the 2 strands might separate during replication with from each one strand serving as a templet from which the new complementary chain for each is copied, generating two double-stranded molecules from one.

Models of Counte

In that respect were threesome models of replication possible from such a scheme: blimpish, semi-conservative, and dispersive. In conservativist rejoinder, the two master DNA strands,  known as the parental strands, would re-basepair with each other after being secondhand as templates to synthesize new strands; and the two newly-synthesized strands, known as the daughter strands, would as wel basepair with apiece separate; one of the two Desoxyribonucleic acid molecules after replication would beryllium "all-old" and the other would be "all-untested". In semi-conservative replication, each of the cardinal maternal DNA strands would bi as a template for new DNA strands to be synthesized, simply later replication, each parental DNA strand would basepair with the complementary recently-synthesized strand just synthesized, and both doubling-isolated DNAs would admit matchless maternal or "old" strand and matchless daughter or "new" strand. In dispersive replication, subsequently replication both copies of the new DNAs would somehow have cyclic segments of paternal DNA and newly-synthesized DNA on each of their two strands.

Recommended Models of DNA Replication: The tercet suggested models of DNA replication. Grey indicates the groundbreaking parental DNA strands  or segments and gentle indicates newly-synthesized daughter DNA strands or segments.

To determine which posture of replication was precise, a seminal experiment was performed in 1958 by two researchers: Matthew Meselson and Franklin Stahl.

Meselson and Stahl

Meselson and Stahl were curious in understanding how DNA replicates. They grew Escherichia coli for several generations in a medium containing a "heavy" isotope of nitrogen (¹⁵N) that is incorporated into nitrogenous bases and, eventually, into the DNA. The E. coli culture was then shifted into medium containing the common "sparkle" isotope of nitrogen (¹⁴N) and allowed to grow for one generation. The cells were harvested and the DNA was isolated. The DNA was centrifuged at high speeds in an ultracentrifuge in a tube in which a cesium chloride denseness gradient had been conventional. Any cells were allowed to grow for one many life history cycle in ¹⁴N and spun over again.

Meselson and Stahl: Meselson and Stahl experimented with E. coli grown first in operose N (¹⁵N) then in ligher nitrogen (¹⁴N.) Desoxyribonucleic acid grown in ¹⁵N (red band) is heavier than DNA grown in ¹⁴N (orange dance orchestra) and sediments to a lower level in the Cs chloride density gradient in an ultracentrifuge. When DNA grown in ¹⁵N is switched to media containing ¹⁴N, later one round of cell division the DNA sediments halfway between the ¹⁵N and ¹⁴N levels, indicating that it now contains fifty per centum ¹⁴N and cardinal percent ¹⁵N.. In subsequent cell divisions, an increasing add up of Desoxyribonucleic acid contains ¹⁴N only. These data support the semi-conservative replication model.

During the density gradient ultracentrifugation, the DNA was loaded into a slope (Meselson and Stahl used a gradient of cesium chloride salt, although different materials so much as saccharose ass also comprise wont to create a slope) and spun at high speeds of 50,000 to 60,000 rpm. In the ultracentrifuge underground, the cesium chloride salt created a density gradient, with the cesium chloride solution being Thomas More dense the farther down the tube you went. Under these lot, during the spin the DNA was pulled refine the ultracentrifuge tube by efferent force until information technology arrived at the spotlight in the salt gradient where the DNA molecules' density matched that of the surrounding table salt resolution. At the point, the molecules stopped sedimenting and acorn-shaped a stable band. By superficial at the congeneric positions of bands of molecules run in the Same gradients, you send away determine the relative densities of different molecules. The molecules that form the lowest bands have the highest densities.

DNA from cells grown exclusively in ¹⁵N produced a lower band than DNA from cells grown exclusively in ¹⁴N. So DNA grown in ¹⁵N had a high density, A would be anticipated of a molecule with a heavier isotope of N incorporated into its gas bases. Meselson and Stahl noted that after one generation of growth in ¹⁴N (after cells had been shifted from ¹⁵N), the DNA molecules produced only single band intermediate in position in between DNA of cells grown only in ¹⁵N and DNA of cells grown exclusively in ¹⁴N. This suggested either a semi-conservative operating theatre dispersive mode of replication. Conservative replication would have resulted in two bands; one representing the paternal Desoxyribonucleic acid still with exclusively ¹⁵N in its nitrogenous bases and the other representing the girl DNA with alone ¹⁴N in its nitrogen-bearing bases. The single band really seen indicated that all the DNA molecules contained equal amounts of both ¹⁵N and ¹⁴N.

The DNA harvested from cells grown for cardinal generations in ¹⁴N formed two bands: unrivalled DNA band was at the intermediate position 'tween ¹⁵N and ¹⁴N and the other corresponded to the band of exclusively ¹⁴N DNA. These results could only be explained if DNA replicates in a semitrailer-conservative manner. Dispersive riposte would have resulted in exclusively a single band in each new generation, with the band slowly moving heavenward closer to the height of the ¹⁴N DNA band. Thence, dispersive rejoinder could also be ruled out.

Meselson and Stahl's results established that during Desoxyribonucleic acid replication, each of the two strands that stimulate up the double helix serves every bit a template from which new strands are synthesized. The new Strand will be complementary to the parental operating room "old" strand and the new strand testament remain basepaired to the old strand. So each "daughter" DNA actually consists of one "old"  DNA strand and one newly-synthesized strand. When two daughter DNA copies are bacillar, they have the congruent sequences to one another and identical sequences to the original maternal DNA, and the deuce daughter DNAs are divided every bit into the 2 daughter cells, producing daughter cells that are genetically monovular to one another and genetically identical to the parent cell.

DNA Replication in Prokaryotes

Prokaryotic DNA is replicated past Desoxyribonucleic acid polymerase III in the 5′ to 3′ centering at a rank of 1000 nucleotides per second.

Learning Objectives

Excuse the functions of the enzymes involved in procaryotic DNA replication

Key Takeaways

Key Points

• Helicase separates the DNA to form a rejoinder fork at the origin of replication where DNA replication begins.
• Replication forks extend Bi-directionally as replication continues.
• Okazaki fragments are v-shaped on the lagging strand, while the leadership strand is replicated continuously.
• Desoxyribonucleic acid ligase seals the gaps between the Okazaki fragments.
• Primase synthesizes an RNA primer with a free 3′-OH, which DNA polymerase III uses to synthesise the daughter strands.

Key Terms

• DNA replication: a natural unconscious process occuring in all keep organisms that is the basis for biological inheritance
• helicase: an enzyme that unwinds the DNA whorl forward of the replication machinery
• origin of replication: a particular sequence in a genome at which replication is initiated

DNA Replication in Prokaryotes

DNA replication employs a multitude of proteins and enzymes, for each one of which plays a critical role during the process. One of the discover players is the enzyme Deoxyribonucleic acid polymerase, which adds nucleotides one by unitary to the growing DNA mountain range that are complemental to the template strand. The addition of nucleotides requires muscularity; this energy is obtained from the nucleotides that rich person three phosphates attached to them, similar to ATP which has deuce-ac orthophosphate groups sessile. When the bond between the phosphates is broken, the Energy Department released is wont to form the phosphodiester alliance between the incoming nucleotide and the growing chain. In prokaryotes, three primary types of polymerases are known: DNA pol I, DNA politician II, and DNA politico Tercet. DNA pol III is the enzyme required for DNA synthesis; DNA politician I and Desoxyribonucleic acid pol II are principally required for repair.

There are specific nucleotide sequences called origins of replication where comeback begins. In E. coli, which has a single origin of replication on its one chromosome (as do about prokaryotes), IT is close to 245 base pairs long and is ample in AT sequences. The origin of replication is recognized away certain proteins that bind to this site. An enzyme known as helicase unwinds the DNA by breaking the hydrogen bonds between the nitrogenous base pairs. ATP hydrolysis is required for this cognitive process. As the DNA opens up, Y-shaped structures known as replication forks are formed. 2 replication forks at the origin of replication are extended bi-directionally as replication proceeds. Single-strand binding proteins surface the strands of DNA near the replication fork to forbid the single-stranded DNA from twist back into a doubling helix. DNA polymerase is able to add together nucleotides solely in the 5′ to 3′ direction (a new DNA Strand can be extended only in this direction). It also requires a free 3′-OH aggroup to which it bum add nucleotides past forming a phosphodiester bond between the 3′-OH end and the 5′ phosphate of the next nucleotide. This means that it cannot add nucleotides if a free 3′-OH chemical group is non available. Some other enzyme, RNA primase, synthesizes an RNA primer that is about five to ten nucleotides overnight and complementary to the Deoxyribonucleic acid, priming DNA synthesis. A primer provides the free 3′-Ohio end to originate replication. DNA polymerase and then extends this RNA primer, adding nucleotides one by one and only that are complementary to the guide strand.

DNA Replication in Prokaryotes: A replication pitchfork is formed when helicase separates the DNA strands at the origination of replication. The DNA tends to become much highly whorled ahead of the replication fork. Topoisomerase breaks and reforms DNA's phosphate backbone ahead of the reverberation fork, thereby relieving the pressure that results from this supercoiling. Single-fibril book binding proteins bind to the single-stranded DNA to prevent the helix from atomic number 75-forming. Primase synthesizes an RNA primer. DNA polymerase Threesome uses this undercoat to synthesize the daughter DNA strand. On the leading Strand, DNA is synthesized unceasingly, whereas on the lagging strand, DNA is synthesized in short stretches called Okazaki fragments. DNA polymerase I replaces the RNA primer with DNA. DNA ligase seals the gaps between the Okazaki fragments, connection the fragments into a single DNA molecule.

The replication fork moves at the range of 1000 nucleotides per second. Deoxyribonucleic acid polymerase can only extend in the 5′ to 3′ direction, which poses a svelte problem at the replication separate. As we know, the Deoxyribonucleic acid double helix is anti-parallel; that is, one strand is in the 5′ to 3′ direction and the other is orientating in the 3′ to 5′ focus. One strand (the major fibril), complementary to the 3′ to 5′ parental Desoxyribonucleic acid strand, is synthesized continuously towards the replication fork because the polymerase can minimal brain dysfunction nucleotides in this direction. The other strand (the lagging strand), complementary to the 5′ to 3′ parental DNA, is extended away from the replication fork in small fragments known equally Okazaki fragments, each requiring a fusee to start the synthetic thinking. Okazaki fragments are named later the Nipponese man of science who early determined them.

The leading maroon can be extended by one primer alone, whereas the lagging strand needs a new fuze for each of the short Okazaki fragments. The overall direction of the lagging maroon will be 3′ to 5′, while that of the leading strand will Be 5′ to 3′. The sliding clamp (a annulate protein that binds to the DNA) holds the DNA polymerase in place as information technology continues to add nucleotides. Topoisomerase prevents the over-winding of the DNA double whorl ahead of the replication separate as the DNA is opening up; information technology does so by causing temporary nicks in the DNA volute and then resealing it. As synthesis payof, the RNA primers are replaced by DNA. The primers are removed by the exonuclease natural action of DNA political leader I, while the gaps are filled in aside deoxyribonucleotides. The nicks that remain between the newly-synthesized DNA (that replaced the RNA primer) and the previously-synthesized Deoxyribonucleic acid are sealed away the enzyme DNA ligase that catalyzes the formation of phosphodiester linkage between the 3′-OH end of one nucleotide and the 5′ phosphate closing of the other fragment.

The table summarizes the enzymes involved in prokaryotic DNA replication and the functions of from each one.

Being DNA Replication: Enzymes and Their Function: The enzymes involved in prokaryotic Desoxyribonucleic acid replication and their functions are summarized on this table.

DNA Echo in Eukaryotes

DNA replication in eukaryotes occurs in terzetto stages: initiation, elongation, and termination, which are aided aside some enzymes.

Scholarship Objectives

Distinguish how DNA is replicated in eukaryotes

Key Takeaways

Key Points

• During initiation, proteins bind to the bloodline of replication while helicase unwinds the DNA helix and two riposte forks are formed at the origin of riposte.
• During elongation, a primer sequence is added with additive RNA nucleotides, which are then replaced away DNA nucleotides.
• During elongation the lead strand is made continuously, while the lagging string is ready-made in pieces called Okazaki fragments.
• During termination, primers are removed and replaced with rising DNA nucleotides and the backbone is sealed by Desoxyribonucleic acid ligase.

Key Damage

• origin of replication: a fastidious chronological succession in a genome at which sound reflection is initiated
• leading strand: the template strand of the DNA double helix that is oriented so that the replication fork moves along it in the 3′ to 5′ focus
• lagging Strand: the Strand of the templet DNA double volute that is oriented so that the replication fork moves along IT in a 5′ to 3′ personal manner

Because eukaryotic genomes are quite interwoven, DNA replication is a very complicated mental process that involves several enzymes and other proteins. IT occurs in three main stages: initiation, elongation, and termination.

Initiation

Eukaryotic Desoxyribonucleic acid is bound to proteins titled histones to form structures known as nucleosomes. During initiation, the Deoxyribonucleic acid is ready-made accessible to the proteins and enzymes involved in the replication process. There are specific chromosomal locations called origins of return where return begins. In some eukaryotes, like yeast, these locations are defined by having a specific sequence of basepairs to which the reproduction initiation proteins bind. In other eukaryotes, like humans, there does not appear to comprise a consensus sequence for their origins of replication. Instead, the replication knowledgeability proteins might identify and bind to specific modifications to the nucleosomes in the root region.

Certain proteins recognize and bind to the stemma of replication and then allow the other proteins necessary for DNA replication to attach the same region. The first proteins to bind the DNA are said to "recruit" the other proteins. Two copies of an enzyme called helicase are among the proteins recruited to the origin. Each helicase unwinds and separates the DNA helix into fibre DNA. As the DNA opens up, Y-shaped structures called replication forks are formed. Because two helicases bind, deuce replication forks are formed at the origin of replication; these are large in both directions as replication proceeds creating a replication bubble. There are ninefold origins of replication happening the eukaryotic chromosome which allow replication to occur at the same time in hundreds to thousands of locations on apiece chromosome.

Replication Fork Formation: A replication fork is formed past the opening of the origin of replica; helicase separates the Desoxyribonucleic acid strands. An RNA primer is synthesized by primase and is elongated by the DNA polymerase. On the leading strand, only a single RNA primer is requisite, and DNA is synthesized continuously, whereas on the lagging strand, DNA is synthesized in short stretches, each of which must start with its own RNA priming coat. The DNA fragments are joined by DNA ligase (not shown).

Elongation

During elongation, an enzyme named DNA polymerase adds Deoxyribonucleic acid nucleotides to the 3′ end of the newly synthesized polynucleotide fibril. The template Strand specifies which of the four DNA nucleotides (A, T, C, or G) is added at apiece positioning along the new chain. Only the nucleotide additive to the template nucleotide at that set out is added to the new strand.

DNA polymerase contains a rut that allows information technology to bind to a single-unaccompanied template Deoxyribonucleic acid and travel 1 nucleotide at at time. For lesson, when DNA polymerase meets an adenosine nucleotide on the template Strand, IT adds a thymidine to the 3′ end of the freshly synthesized maroon, and and then moves to the next nucleotide on the guide strand. This procedure bequeath continue until the DNA polymerase reaches the end of the template strand.

DNA polymerase cannot initiate new strand synthesis; it only adds new nucleotides at the 3′ close of an existing strand. All freshly synthesized polynucleotide strands must be initiated past a specialized Ribonucleic acid polymerase called primase. Primase initiates polynucleotide synthesis and away creating a short RNA polynucleotide strand complementary to template DNA strand. This short stretch of Ribonucleic acid nucleotides is called the primer. In one case RNA primer has been synthesized at the template DNA, primase exits, and DNA polymerase extends the new strand with nucleotides complementary to the template DNA.

At length, the RNA nucleotides in the primer are distant and replaced with DNA nucleotides. Once DNA replication is finished, the daughter molecules are successful entirely of unbroken DNA nucleotides, with no Ribonucleic acid portions.

The Leading and Lagging Strands

DNA polymerase can merely synthesize other strands in the 5′ to 3′ direction. Therefore, the two newly-synthesized strands grow in opposition directions because the templet strands at each replication fork are antiparallel. The "leading strand" is synthesized continuously toward the replication fork as helicase unwinds the template double-stranded DNA.

The "lagging strand" is synthesized in the direction away from the replication fork and away from the DNA helicase unwinds. This lagging strand is synthesized in pieces because the Deoxyribonucleic acid polymerase can only synthesize in the 5′ to 3′ focussing, and soh it constantly encounters the previously-synthesized new strand. The pieces are called Okazaki fragments, and from each one fragment begins with its own RNA primer.

Termination

Eukaryotic chromosomes have multiple origins of replication, which pioneer replication almost simultaneously. Each origin of replication forms a bubble of duplicated DNA connected either side of the origin of replication. Eventually, the leading strand of one return bubble reaches the lagging strand of another bubble, and the lagging strand will give the 5′ end of the previous Okazaki break up in the same bubble.

Desoxyribonucleic acid polymerase halts when it reaches a plane section of DNA template that has already been replicated. However, DNA polymerase cannot catalyze the organization of a phosphodiester bond 'tween the two segments of the new DNA strand, and it drops sour. These unattached sections of the sugar-phosphate backbone in an other than heavy-replicated DNA strand are named nicks.

Once all the template nucleotides have been replicated, the replication cognitive operation is non yet over. RNA primers need to be replaced with DNA, and nicks in the sugar-phosphate backbone need to be connected.

The chemical group of cancellous enzymes that remove RNA primers admit the proteins FEN1 (flap endonulcease 1) and Ribonuclease H. The enzymes FEN1 and RNase H transfer Ribonucleic acid primers at the start of each leading strand and at the start of each Okazaki sherd, leaving gaps of unreplicated template Deoxyribonucleic acid. Once the primers are removed, a free-floating DNA polymerase lands at the 3′ end of the preceding DNA fragment and extends the DNA over the gap. Yet, this creates new nicks (detached sugar-phosphate spinal column).

In the end of DNA reproduction, the enyzme ligase joins the sugar-phosphate backbones at each nick site. After ligase has connected all nicks, the new filament is one long continuous DNA strand, and the girl DNA molecule is complete.

DNA Replication: This is a clip from a PBS yield called "DNA: The Secret of Life." It details the latest research (as of 2005) concerning the outgrowth of DNA replication.

Telomere Reproduction

Equally DNA polymerase alone cannot replicate the ends of chromosomes, telomerase aids in their replication and prevents chromosome degradation.

Learning Objectives

Identify the role played by telomerase in replication of telomeres

Key Takeaways

Key Points

• DNA polymerase cannot replicate and repair DNA molecules at the ends of linear chromosomes.
• The ends of linear chromosomes, called telomeres, protect genes from getting deleted as cells continue to watershed.
• The telomerase enzyme attaches to the end of the chromosome; complementary bases to the RNA guide are added connected the 3′ end of the Desoxyribonucleic acid string.
• Once the lagging strand is long by telomerase, DNA polymerase fundament add the completing nucleotides to the ends of the chromosomes and the telomeres can finally be replicated.
• Cells that undergo cell partition continue to have their telomeres sawed-off because most somatic cells do not make telomerase; telomere shortening is associated with ripening.
• Telomerase reactivation in telomerase-deficient mice causes extension of telomeres; this may have potential for treating age-related diseases in humans.

Key Terms

• telomere: either of the repetitious nucleotide sequences at each end of a eukaryotic chromosome, which protect the chromosome from debasement
• telomerase: an enzyme in eukaryotic cells that adds a specific chronological succession of Desoxyribonucleic acid to the telomeres of chromosomes after they divide, giving the chromosomes constancy all over time

The Conclusion Job of Linear DNA Replication

Linear chromosomes have an end problem. Subsequently DNA replication, each newly synthesized DNA chain is shorter at its 5′ end than at the parental DNA strand's 5′ end. This produces a 3′ overhang at ane terminate (and one end only) of all daughter DNA strand, much that the two daughter DNAs have their 3′ overhangs at opposite ends

The telomere end problem: A easy nonrepresentational of DNA replication where the parental DNA (height) is replicated from three origins of replication, yielding three return bubbles (midway) before giving rise to cardinal daughter DNAs (bottom). Paternal DNA strands are black, newly synthesized DNA strands are profane, and Ribonucleic acid primers are Red River. Altogether Ribonucleic acid primers bequeath be removed by Rnase H and FEN1, leaving gaps in the newly-synthesized DNA strands (not shown.) DNA Polymerase and Ligase will replace all the RNA primers with DNA except the RNA primer at the 5′ ends of each fresh-synthesized (blasphemous) strand. This means that each newly-synthesized DNA strand is shorter at its 5′ end than the equivalent strand in the parental DNA.

All RNA primer synthesized during replication can be remote and replaced with Desoxyribonucleic acid strands except the RNA primer at the 5′ end of the newly synthesized string. This small section of RNA can sole be far, not replaced with DNA. Enzymes RNase H and FEN1 get rid of RNA primers, but Deoxyribonucleic acid Polymerase will add new DNA only if the DNA Polymerase has an existing strand 5′ to information technology ("behind" information technology) to extend. However, thither is no more DNA in the 5′ direction after the final RNA primer, so DNA polymerse cannot replace the RNA with DNA. Therefore, both daughter DNA strands have an incomplete 5′ strand with 3′ overhang.

In the absence of additional cellular processes, nucleases would digest these mateless-marooned 3′ overhangs. Each daughter DNA would get along shorter than the parental DNA, and eventually entire Desoxyribonucleic acid would be lost. To forestall this shortening, the ends of linear eukaryotic chromosomes have special structures called telomeres.

Telomere Replication

The ends of the linear chromosomes are well-known As telomeres: repetitious sequences that code for no particular gene. These telomeres protect the important genes from existence deleted as cells divide and equally DNA strands shorten during replication.

In humans, a six cornerstone geminate sequence, TTAGGG, is perennial 100 to 1000 multiplication. After each round of DNA replication, some telomeric sequences are lost at the 5′ end of the newly synthesized strand on each girl DNA, but because these are noncoding sequences, their loss does not adversely bear upon the cell. However, justified these sequences are not unlimited. Aft sufficient rounds of reproduction, all the telomeric repeats are lost, and the Deoxyribonucleic acid risks losing coding sequences with resultant rounds.

The find of the enzyme telomerase helped in the understanding of how chromosome ends are maintained. The telomerase enzyme attaches to the end of a chromosome and contains a chemical process part and a built-in RNA template. Telomerase adds completing RNA bases to the 3′ end of the DNA Strand. Once the 3′ end of the lagging strand templet is sufficiently elongated, DNA polymerase adds the complementary nucleotides to the ends of the chromosomes; olibanum, the ends of the chromosomes are replicated.

Telomerase is important for maintaining chromosome integrity: The ends of linear chromosomes are maintained past the action of the telomerase enzyme.

Telomerase and Senescent

Telomerase is typically open in germ cells and adult stem turn cells, but is not hot in adult somatic cells. As a outcome, telomerase does not protect the DNA of adult bodily cells and their telomeres continually shorten as they go through rounds of cell division.

In 2010, scientists found that telomerase bottom reverse some age-related conditions in mice. These findings may chip in to the future of regenerative medicament. In the studies, the scientists used telomerase-deficient mice with tissue paper atrophy, stem cubicle depletion, organ bankruptcy, and impaired tissue injury responses. Telomerase reactivation in these mice caused extension of telomeres, reduced DNA damage, reversed neurodegeneration, and developed the subroutine of the testes, spleen, and intestines. Thus, telomere reactivation may have potential for treating related to diseases in human race.

Where Does the Phosphodiester Bond Connect the Two Nucleotides?

Source: https://courses.lumenlearning.com/boundless-biology/chapter/dna-replication/

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