DNA Replication and Structure

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Questions and Answers

What is the composition of each daughter DNA molecule?

Two old strands

One old strand and two new strands

One old strand and one new strand (correct)

Two new strands

What is the base pairing rule in DNA replication?

Adenine pairs with Guanine

Guanine pairs with Thymine

Adenine pairs only with Thymine (correct)

Cytosine pairs with Adenine

What is the direction of the complementary strand in DNA replication?

Parallel to the template strand

Opposite direction of the template strand (correct)

Same direction as the template strand

Perpendicular to the template strand

What is the function of DNA polymerase in DNA replication?

Synthesis of new DNA strands Signup and view all the answers

What is the role of DNA ligase in DNA replication?

Joining Okazaki fragments Signup and view all the answers

What is the direction of DNA synthesis?

5' to 3' direction Signup and view all the answers

What is the function of topoisomerase in DNA replication?

Relieving torsional strain Signup and view all the answers

What is the requirement for DNA synthesis?

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

What is the direction of DNA synthesis in the leading strand?

5´- 3´ direction Signup and view all the answers

What is the function of the primase enzyme?

To synthesize a short stretch of RNA complementary to the template DNA strands Signup and view all the answers

What is the role of DNA polymerase ε in replication?

To synthesize the leading strand Signup and view all the answers

What is the function of ligase enzyme in replication?

To connect Okazaki fragments into one continuous strand Signup and view all the answers

What is the direction of DNA synthesis in the lagging strand?

Direction away from the replication fork Signup and view all the answers

What are Okazaki fragments?

Small DNA segments synthesized in a discontinuous manner Signup and view all the answers

What is the direction of the replication fork movement?

Towards Ori Signup and view all the answers

What is the direction of DNA polymerase δ synthesis in the lagging strand?

In the opposite direction of the advancing replication fork Signup and view all the answers

What is the primary function of helicase enzymes in DNA replication?

To break the hydrogen bonds between DNA strands Signup and view all the answers

What is the purpose of topoisomerase enzymes in DNA replication?

To solve the problem of supercoiling Signup and view all the answers

What is the characteristic of the short sequence at the origin of replication?

Composed only of AT base pairs Signup and view all the answers

What is the role of single-stranded binding proteins in DNA replication?

To keep the two strands of DNA apart Signup and view all the answers

What is the shape of the structure formed during DNA replication?

V-shaped Signup and view all the answers

What is the problem that occurs in the region of DNA ahead of the replication fork?

Supercoiling Signup and view all the answers

What is the function of the primer in DNA replication?

To initiate DNA synthesis Signup and view all the answers

What is the direction of DNA synthesis in semi-conservative replication?

5´-3´ Signup and view all the answers

Study Notes

Structure of DNA

Each daughter DNA molecule consists of one old strand (parental strand) and one new strand (from free nucleotides in the nucleus)
The base pairing rule is maintained: Adenine pairs with Thymine (A-T, two H bonds) and Cytosine pairs with Guanine (C-G, three H bonds)
A + G = T + C in DNA molecule

Replication Process

Replication is a bidirectional process that proceeds in both directions
Synthesis of new strand occurs in 5' to 3' direction by DNA polymerase
The process requires a template, primer, and substrates (dATP, dGTP, dCTP, and dTTP)

Enzymes and Proteins Involved

DNA helicases: unwind double-stranded DNA
Single-stranded DNA binding protein (ssDB): stabilizes single-stranded DNA
Primase: synthesizes RNA primer
DNA polymerase: chief enzyme for DNA chain elongation, repair, and proofreading
DNA ligase: joins Okazaki fragments
Topoisomerase: relieves torsional strain by cutting and joining single strands or both strands

Steps of DNA Replication

Identification of the origin of replication
Unwinding of double-stranded DNA by DNA helicase
Binding of single-stranded DNA by ssDB
Synthesis of RNA primer by primase
Synthesis of new DNA strand by DNA polymerase
Proofreading and repair by DNA polymerase
Ligation of newly synthesized DNA segments by DNA ligase

Leading Strand and Lagging Strand

Leading strand: synthesized continuously in 5' to 3' direction by DNA polymerase ε
Lagging strand: synthesized discontinuously in short fragments (Okazaki fragments) by DNA polymerase δ

Primers Removal and Ligation

Excision of RNA primers by exonucleases
Removal of RNA primers and ligation of newly synthesized DNA segments by DNA ligase

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Description

This quiz covers the process of DNA replication, including the conservation of one parent strand, the formation of a new strand, and the importance of base pairing rules. It also touches on the anti-parallel structure of DNA strands.