DNA Replication Enzymes and Structure

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Questions and Answers

What is DNA ligase?

An enzyme essential for DNA replication (correct)

A unit of hereditary information

A type of DNA polymerase

A structure in the DNA molecule

What is the role of DNA polymerase I?

Catalyzes elongation of new DNA and replaces RNA nucleotides.

What does DNA polymerase III do?

Catalyzes elongation of new DNA by adding nucleotides.

The double helix refers to the structure of DNA.

True Signup and view all the answers

What is the function of helicase?

Untwists the double helix of DNA at the replication forks. Signup and view all the answers

What is the lagging strand?

A discontinuously synthesized DNA strand. Signup and view all the answers

Describe the leading strand.

The new continuous complementary DNA strand. Signup and view all the answers

What is mismatch repair?

The process that fixes incorrectly paired nucleotides. Signup and view all the answers

What is a nuclease?

A team of enzymes that hydrolyze DNA and RNA. Signup and view all the answers

What does nucleotide excision repair involve?

Removing and replacing a damaged segment of DNA. Signup and view all the answers

What are Okazaki fragments?

Fragments of the lagging strand of synthesized DNA. Signup and view all the answers

What is the origin of replication?

Sites where the replication of a DNA molecule begins. Signup and view all the answers

What does primase do?

Joins RNA nucleotides to make the primer. Signup and view all the answers

What is an RNA primer?

An existing RNA chain bound to a template DNA. Signup and view all the answers

What is a replication fork?

A Y-shaped region on a replicating DNA molecule. Signup and view all the answers

What is the semiconservative model of DNA replication?

A model in which the replicated double helix consists of one old and one new strand. Signup and view all the answers

What is the function of single strand binding protein (SSBP)?

Holds unpaired DNA strands apart during replication. Signup and view all the answers

What does telomerase do?

Catalyzes the lengthening of telomeres. Signup and view all the answers

What is a telomere?

The protective structure at the end of a eukaryotic chromosome. Signup and view all the answers

What is the role of topoisomerase (gyrase)?

Helps relieve strain from twisting DNA strands. Signup and view all the answers

Study Notes

DNA Replication Enzymes

DNA ligase: Links DNA fragments by covalently bonding the 3' end of a new fragment to the 5' end of a growing DNA chain.
DNA polymerase I: Adds nucleotides to a growing DNA strand at the replication fork and replaces RNA nucleotides in the RNA primer with DNA.
DNA polymerase III: Responsible for elongating DNA by adding nucleotides to the 3' end of pre-existing strands or RNA primers.
Primase: Synthesizes RNA primers by joining RNA nucleotides, providing a starting point for DNA synthesis.
Nuclease: Enzymes that break down DNA and RNA into individual nucleotides by hydrolysis.
Telomerase: Lengthens telomeres, containing RNA that serves as a template for new telomere DNA segments.

DNA Structure and Function

Double helix: The native form of DNA, consisting of two polynucleotide strands coiled in a spiral formation.
Telomeres: Repetitive DNA sequences at the ends of eukaryotic chromosomes that protect against degradation.
Single strand binding protein (SSBP): Stabilizes unpaired DNA strands during replication, ensuring they remain open for complementary strand synthesis.

DNA Replication Processes

Leading strand: Synthesized continuously in the 5' to 3' direction along the template strand.
Lagging strand: Synthesized discontinuously, creating Okazaki fragments that are later joined by DNA ligase.
Replication fork: The Y-shaped area on a replicating DNA molecule where new strands are forming.
Origin of replication: The specific sites where DNA replication begins.
Okazaki fragments: Short sections of synthesized DNA (100-200 nucleotides) on the lagging strand that must be connected by DNA ligase.

DNA Repair Mechanisms

Mismatch repair: A process where enzymes fix incorrectly paired nucleotides during DNA replication.
Nucleotide excision repair: Removes and replaces damaged segments of DNA using the undamaged strand as a template.

Additional Proteins in DNA Replication

Helicase: Enzyme that unwinds the double helix, creating replication forks.
Topoisomerase (gyrase): Relieves strain ahead of helicase by managing DNA supercoiling.

Concepts of DNA Replication

Semiconservative model: Each resulting DNA molecule consists of one parent strand and one newly synthesized strand, preserving half of the original DNA.

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Description

Explore the essential enzymes involved in DNA replication and learn about the unique structure of DNA, including its double helix formation and the role of telomeres. This quiz covers key concepts related to DNA synthesis and function in cellular processes.