DNA Replication Steps Flashcards

Questions and Answers

What is DNA replication?

The process of RNA synthesis.

The process of protein synthesis.

The process of DNA being destroyed.

The process by which DNA makes a copy of itself during cell division. (correct)

What happens in Step 1 of DNA replication?

Helicase opens up the two strands of the double helix.

What is the function of single strand binding proteins in Step 2?

They keep the two strands open.

What does topoisomerase do in Step 3 of DNA replication?

Unwinds the strands and prevents them from twisting. Signup and view all the answers

What role does primase play in Step 4 of DNA replication?

It puts an RNA primer at the beginning of the replication. Signup and view all the answers

What distinguishes the leading strand from the lagging strand in Step 5?

The leading strand is oriented in the 3' to 5' direction toward the replication fork, while the lagging strand goes 5' to 3' away from the fork. Signup and view all the answers

What does DNA polymerase do in Step 6?

It binds to the leading strand and elongates it by adding new complementary nucleotide bases. Signup and view all the answers

What are Okazaki fragments and how are they formed in Step 7?

Okazaki fragments are short fragments formed on the lagging strand which go 5' to 3' in pieces. Signup and view all the answers

What is the role of DNA ligase in Step 8?

It seals up the sequence into two continuous double strands. Signup and view all the answers

What is the final result of DNA replication?

Two DNA molecules consisting of one new and one old chain of nucleotides. Signup and view all the answers

Study Notes

DNA Replication Overview

DNA replication occurs during the "S" phase of the cell cycle, allowing cells to duplicate their genetic material.
The double helix structure consists of two strands: a leading strand running 5' to 3' and a lagging strand running 3' to 5'.

Step 1: Helicase Action

Helicase enzyme unwinds and separates the two strands of the DNA double helix.

Step 2: Stability of Strands

Single-strand binding proteins stabilize and keep the separated strands open, preventing them from re-annealing.

Step 3: Topoisomerase Function

Topoisomerase mitigates tension by unwinding coiling strands, forming a replication fork with a Y shape where DNA is separated for replication.

Step 4: RNA Primer Addition

Primase enzyme synthesizes an RNA primer that initiates the replication process on the DNA strands.

Step 5: Distinction Between Strands

Leading strand is oriented towards the replication fork (3' to 5'), allowing continuous synthesis in 5' to 3' direction.
Lagging strand is oriented away from the replication fork (5' to 3'), necessitating discontinuous synthesis in small fragments known as Okazaki fragments.

Step 6: Leading Strand Synthesis

DNA polymerase attaches to the leading strand and synthesizes the new strand by adding complementary nucleotides (A, C, G, T) in a 5' to 3' direction.

Step 7: Lagging Strand Fragmentation

Lagging strand synthesis occurs in fragments (Okazaki fragments), requiring multiple RNA primers. Enzymes later remove these primers and fill in the gaps.

Step 8: Sealing of Strands

DNA Ligase enzyme connects the Okazaki fragments, creating two continuous double strands of DNA.

Final Result of DNA Replication

The outcome is two identical DNA molecules, each comprising one original and one newly synthesized strand, demonstrating the semi-conservative nature of DNA replication. The strands naturally coalesce back into a double helix structure.

Description

This quiz covers the essential steps of DNA replication, a crucial process in cell division. Learn about the roles of helicase and single strand binding proteins, among other key components. Perfect for biology students looking to reinforce their knowledge.