What is telomere replication?
Telomeres are the physical ends of eukaryotic chromosomes. They protect chromosome ends from DNA degradation, recombination, and DNA end fusions, and they are important for nuclear architecture. Telomeres provide a mechanism for their replication by semiconservative DNA replication and length maintenance by telomerase.
What is the job of topoisomerase?
Topoisomerase is a valuable enzyme for untangling supercoils and making space for new DNA strands to be created. Topoisomerase can both cleave DNA at a desired replication site and also ligate the DNA once the process is complete.
What are Primases in DNA replication?
Primase functions by synthesizing short RNA sequences that are complementary to a single-stranded piece of DNA, which serves as its template. It is critical that primers are synthesized by primase before DNA replication can occur.
How does replication initiation in E coli?
To initiate DNA replication, DnaA recognizes and binds to specific sequences within the Escherichia coli chromosomal origin (oriC), and then unwinds a region within oriC. Next, DnaA interacts with DnaB helicase in loading the DnaB-DnaC complex on each separated strand.
What is telomere and its function?
These are little protective caps at the ends of the DNA molecules that make up our chromosomes. Their job is to stop the ends of chromosomes from fraying or sticking to each other, much like the plastic tips on the ends of shoelaces.
What is the telomere replication problem?
At each cell division, the telomeres shorten because of the incomplete replication of the linear DNA molecules by the conventional DNA polymerases. This is called the end replication problem [6]. This is specifically due to the resection and fill-in reaction during the synthesis of the telomere leading-strand [7,8].
What is the function of topoisomerases in replication of DNA?
function in DNA replication A class of enzymes called DNA topoisomerases removes helical twists by cutting a DNA strand and then resealing the cut. Enzymes called helicases then separate the two strands of the double helix, exposing two template surfaces for the alignment of free nucleotides.
What does topoisomerase do in replication?
Abstract. DNA topoisomerases solve the topological problems associated with DNA replication, transcription, recombination, and chromatin remodeling by introducing temporary single- or double-strand breaks in the DNA.
What does semi conservative mean in DNA?
Definition of semiconservative : relating to or being genetic replication in which a double-stranded molecule of nucleic acid separates into two single strands each of which serves as a template for the formation of a complementary strand that together with the template forms a complete molecule.
Why is DNA replication called a semi conservative process?
DNA replication is semi-conservative because each helix that is created contains one strand from the helix from which it was copied. The replication of one helix results in two daughter helices each of which contains one of the original parental helical strands.
What is initiation of replication?
The initiation of chromosomal DNA replication starts at a replication origin, which in bacteria is a discrete locus that contains DNA sequence motifs recognized by an initiator protein whose role is to assemble the replication fork machinery at this site.
How is DNA replication in E. coli?
Abstract. DNA replication in Escherichia coli initiates at oriC, the origin of replication and proceeds bidirectionally, resulting in two replication forks that travel in opposite directions from the origin. Here, we focus on events at the replication fork.
What telomere means?
A telomere is a region of repetitive DNA sequences at the end of a chromosome. Telomeres protect the ends of chromosomes from becoming frayed or tangled. Each time a cell divides, the telomeres become slightly shorter.
What are two important functions of telomeres?
Their job is to stop the ends of chromosomes from fraying or sticking to each other, much like the plastic tips on the ends of shoelaces. Telomeres also play an important role in making sure our DNA gets copied properly when cells divide.
What are the functions of topoisomerases and Gyrases?
Gyrase is involved primarily in supporting nascent chain elongation during replication of the chromosome, whereas topoisomerase IV separates the topologically linked daughter chromosomes during the terminal stage of DNA replication.
What is the function of topoisomerase 1 and 2?
Definition. Topoisomerase I refers to the enzymes which cut one of the two strands of double-stranded DNA, relax the strand, and reanneal the strand while topoisomerase II refers to the enzymes which cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils.
What is the role of topoisomerases in eukaryotic DNA replication quizlet?
What is the function of the enzyme topoisomerase in DNA replication? relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix (Topoisomerases are enzymes that participate in the over winding or underwinding of DNA.
What is difference between DNA helicase and topoisomerase?
Helicases are enzymes that separate the nucleic acid strands for replication. Topoisomerases are enzymes that relax the supercoiling in DNA strands. It utilises energy from the hydrolysis of nucleoside triphosphates to translocate through the DNA strands.
Why is it called semi-conservative replication?
DNA replication: A complex process whereby the ‘parent’ strands of DNA in the double helix are separated, and each one is copied to produce a new (daughter) strand. This process is said to be ‘semiconservative’ because one strand from each parent is conserved and remains intact after replication has taken place.
What is the difference between conservative and Semiconservative DNA replication?
Conservative replication produces two helices, one containing entirely old DNA while the other containing entirely new DNA. Semiconservative replication is the accepted theory of DNA replication that produces two helices, each containing one old strand and one new strand.
Qu’est-ce que la réplication de l’ARN?
La réplication de l’ARN est le processus par lequel de nouvelles copies d’ARN génomique sont produites (figure 8). La réplication de l’ARN a lieu dans le cytoplasme et elle est réalisée par l’ARN polymérase virale.
Comment la réplication de l’ARN a-t-elle lieu dans le cytoplasme?
La réplication de l’ARN a lieu dans le cytoplasme et elle est réalisée par l’ARN polymérase virale. Le choix entre la production des ARNm et de l’ARN brin (+) de longueur génomique est influencé par la présence de la nucléoprotéine virale.
Qu’est-ce que la réplication nucléaire?
Les nucléocapsides sont transportées dans le noyau, et la synthèse des ARNm viraux et la réplication de l’ARN viral sont nucléaires. La réplication nucléaire est très inhabituel pour un virus à ARN. En effet il s’agit d’un caractéristique unique des Orthomyxoviridae – tous les autres virus à ARN se répliquent dans le cytoplasme.
Quelle est la longueur de l’ARN génomique?
L’ARN génomique est brin (-) d’une longueur de 11 à 15 kb codant pour 5 protéines. Exemple : Le virus de la rage.