DNA Replication Process

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Questions and Answers

How many replication bubbles do prokaryotes typically have?

Several

One (correct)

None

Two

In what direction does DNA synthesis proceed with respect to the new daughter strand?

2' - 3'

3' - 5'

5' - 3' (correct)

5' - 5'

What are Okazaki fragments?

Long fragments of RNA produced on the lagging strand

Short fragments of DNA produced by discontinuous synthesis on the leading strand

Fragments of RNA on the leading strand

Short fragments of DNA produced by discontinuous synthesis on the lagging strand (correct)

Which enzyme is responsible for adding nucleotides to a growing DNA strand?

DNA polymerase Signup and view all the answers

Which of the following statements is true about eukaryotic DNA replication?

Eukaryotes have several replication bubbles Signup and view all the answers

What role does the DNA polymerase play in DNA replication?

It adds nucleotides to the growing DNA strand Signup and view all the answers

Where does DNA replication begin?

At the origin of replication Signup and view all the answers

What is produced by RNA primase during DNA replication?

RNA primers Signup and view all the answers

Which enzyme extends DNA on the leading strand?

DNA polymerase III Signup and view all the answers

What are the short fragments synthesized on the lagging strand called?

Okazaki fragments Signup and view all the answers

Which enzyme removes the RNA primer during DNA replication?

DNA polymerase I Signup and view all the answers

What is the role of DNA ligase in DNA replication?

It joins Okazaki fragments Signup and view all the answers

Which statement is true about the replication fork?

It is where the strands of DNA separate Signup and view all the answers

During which step is the 2nd Okazaki fragment synthesized?

Further untwisting and elongation Signup and view all the answers

What is the term for DNA replication that results in each new DNA molecule containing one original strand and one new strand?

Semi-conservative Signup and view all the answers

What provides the catalysis for the 3' hydroxyl group to attack the phosphate of a 5'-deoxynucleoside triphosphate?

DNA polymerase Signup and view all the answers

Which enzyme removes a 'turn' of the DNA and is a critical target for antibiotics?

Topoisomerase Signup and view all the answers

Which enzyme is responsible for breaking hydrogen bonds between complementary base pairs during DNA replication?

DNA helicase Signup and view all the answers

What is required for DNA polymerase to initiate synthesis?

Both a template strand and a primer Signup and view all the answers

Which of these is a function of RNA primase in DNA replication?

Synthesizing a short RNA primer Signup and view all the answers

Which of these is NOT a factor involved in DNA replication?

RNA template Signup and view all the answers

Which of the following enzymes seals the backbone of DNA during DNA replication?

DNA ligase Signup and view all the answers

Study Notes

DNA Replication

The Replication Bubble

DNA replication occurs in a bidirectional manner, resulting in a replication bubble
Prokaryotes have one replication bubble, while eukaryotes have multiple
Two replication forks moving in opposite directions form a replication bubble

Mechanisms of DNA Synthesis

DNA synthesis occurs in two directions: leading strand and lagging strand
Leading strand synthesis is continuous, whereas lagging strand synthesis is discontinuous
Nucleotides are added 5' - 3' along the new daughter strand
DNA polymerase reads 3' - 5' along the leading strand from the RNA primer

DNA Polymerase

DNA polymerase can only add nucleotides to a growing polymer
Part of the replisome complex with other proteins such as PCNA

Process of DNA Replication

The process begins with the unwinding of the double helix at the origin of replication
RNA primase synthesizes a short RNA primer, which is later removed and replaced by DNA
DNA polymerase III extends the DNA strands
Okazaki fragments are formed on the lagging strand
DNA polymerase I removes the RNA primer and replaces it with DNA
DNA ligase joins the adjacent DNA fragments

Okazaki Fragments

Short fragments of DNA produced by discontinuous synthesis on the lagging strand
DNA synthesis on the lagging strand is discontinuous, resulting in Okazaki fragments

Enzymes Involved

DNA Gyrase or Topoisomerase: removes 'turns' of DNA, critical target for blocking cell replication
DNA Helicase: breaks hydrogen bonds between complementary base pairs, forming the replication fork
Single strand binding protein: maintains the stability of the replication fork
RNA Polymerase (RNA Primase): synthesizes a short RNA primer
DNA Polymerase: synthesizes DNA strands
DNA Ligase: joins adjacent DNA fragments

DNA Gyrase

A topoisomerase II enzyme that causes a double-strand break and loops one strand under another
Removes a 'turn' of DNA, critical for cell replication

DNA Helicase

Breaks hydrogen bonds between complementary base pairs, forming the replication fork
Maintains the stability of the replication fork with single strand binding proteins

RNA Primase

Synthesizes a short RNA primer, which is later removed and replaced by DNA
Follows base pairing rules (A-U), later replaced by DNA and sealed by DNA ligase

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Description

This quiz covers the DNA replication process, including the replication bubble, bidirectional synthesis, and the mechanics of DNA synthesis in prokaryotes and eukaryotes.