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What is the replication factory?

What is the replication factory?

DNA replication in human cells is performed in discrete sub-nuclear locations known as replication foci or factories. These factories form in the nucleus during S phase and are sites of DNA synthesis and high local concentrations of enzymes required for chromatin replication.

What is the model of DNA replication called and why?

DNA replication is called semiconservative because an existing DNA strand is used to create a new strand.

What are the different types of DNA replication?

The three models for DNA replication

  • Conservative. Replication produces one helix made entirely of old DNA and one helix made entirely of new DNA.
  • Semi-conservative. Replication produces two helices that contain one old and one new DNA strand.
  • Dispersive.

What is DNA replication with diagram?

The first step of DNA replication is the unwinding parent double helix molecule so that each strand acts as a template for the new strand. Unwinding mechanism is very complex. Hydrogen bonds between two strands are broken. This is achieved by enzymes called DNA helicases which move along DNA and separate the strands.

How many replication factories does a chromosome have?

How many replication factories are there (on average) on each chromosome in the nucleus? 48. Why do the telomeres shorten with each replication? Which cell types have telomerase to lengthen them?

Where is the replication factory found in a eukaryotic cell?

Eukaryotic DNA replication requires multiple replication forks, while prokaryotic replication uses a single origin to rapidly replicate the entire genome. DNA replication always occurs in the nucleus. Eukaryotic DNA replication involves more polymerases than prokaryotic replication.

Why is the Semiconservative model correct?

The semi-conservative model is the intuitively appealing model, because separation of the two strands provides two templates, each of which carries all the information of the original molecule. It also turns out to be the correct one (Meselson & Stahl 1958).

What is Theta model of replication?

A common type of replication that takes place in circular DNA, such as that found in E. coli and other bacteria, is called theta replication because it generates a structure that resembles the Greek letter theta (θ). The unwinding of the double helix generates a loop, termed a replication bubble.

How does DNA replication elongation take place in eukaryotes?

During elongation, a primer sequence is added with complementary RNA nucleotides, which are then replaced by DNA nucleotides. During elongation the leading strand is made continuously, while the lagging strand is made in pieces called Okazaki fragments.

Why DNA replication is called semiconservative?

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.

Which is true of the model of DNA replication?

One strand in each daughter DNA molecule is intact template (parental) and other is an intact newly replicated DNA strand. It is an alternative method of replication. According to this model original double helix of parental DNA molecule is conserved.

How are proteins associated with the replication fork?

A number of proteins are associated with the replication fork to help in the initiation and continuation of DNA synthesis. Most prominently, DNA polymerase synthesizes the new strands by adding nucleotides that complement each (template) strand. DNA replication occurs during the S-stage of interphase .

How does a conservative model of replication work?

In the conservative model, the parental molecule directs synthesis of an entirely new double-stranded molecule, such that after one round of replication, one molecule is conserved as two old strands. This is repeated in the second round.

How does a semi conservative model of DNA work?

In the semi-conservative model, the two parental strands separate and each makes a copy of itself. After one round of replication, the two daughter molecules each comprises one old and one new strand. Note that after two rounds, two of the DNA molecules consist only of new material, while the other two contain one old and one new strand.