DNA Structure and Replication Quiz: Test Your Knowledge

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Questions and Answers

What is the primary difference between the sugar molecules found in DNA and RNA?

Deoxyribose is found in RNA, while ribose is found in DNA

Deoxyribose has a double ring structure, while ribose has a single ring structure

Deoxyribose is found in both DNA and RNA, while ribose is found in neither

Deoxyribose has a single ring structure, while ribose has a double ring structure (correct)

Which of the following nucleotides is NOT a pyrimidine?

A (correct)

What is the primary function of the proteins involved in DNA replication?

To synthesize new nucleotides

To repair damaged DNA

To unwind the double helix and make new, complementary strands (correct)

To transcribe DNA into RNA

What is the term for the process by which DNA is copied, resulting in two double helices, each with one 'old' and one 'new' strand?

Semi-conservative replication Signup and view all the answers

Which of the following is NOT a feature of the Watson-Crick Model of DNA?

Helical structure with sugar-phosphate backbone inside Signup and view all the answers

What is the term for the nucleotides that have a double ring base?

Purines Signup and view all the answers

What is the result of DNA replication?

Two new double helices, each with one 'old' and one 'new' strand Signup and view all the answers

What is the base-pairing rule for DNA, according to the Watson-Crick Model?

A:T; C:G Signup and view all the answers

What is the purpose of the sugar-phosphate backbone in DNA?

To provide structural support for the double helix Signup and view all the answers

What is the term for the process by which new nucleotides are synthesized?

Nucleotide synthesis Signup and view all the answers

What is the primary function of topoisomerase during DNA replication?

To relieve the strain caused by the unwinding of the double helix Signup and view all the answers

What is the role of Primase in the process of DNA replication?

To make a short RNA primer to provide a pre-existing 3'-end Signup and view all the answers

What is the characteristic of the leading strand during DNA replication?

The 3'-end of the daughter DNA is towards the fork Signup and view all the answers

What is the reason for lagging strand synthesis during DNA replication?

The 3'-end of the daughter DNA is away from the fork Signup and view all the answers

What is the function of Ligase in DNA replication?

To link two DNA fragments together with a covalent bond Signup and view all the answers

What is the result of the activity of Primase during DNA replication?

The formation of multiple short DNA fragments Signup and view all the answers

What is the function of DNA polymerase III during DNA replication?

To extend the 3'-end of the primer to make a new DNA strand Signup and view all the answers

What is the role of Helicase during DNA replication?

To break the hydrogen bonds between nucleotides at the replication fork Signup and view all the answers

What is the characteristic of the replication fork during DNA replication?

It consists of two replication forks that move away from each other in opposite directions Signup and view all the answers

What is the function of DNA polymerase I during DNA replication?

To remove the RNA primer and replace it with DNA nucleotides Signup and view all the answers

Study Notes

Nucleic Acids

Cells produce two types of polynucleotides: RNA and DNA
DNA is a polymer of nucleotides A, C, G, and T with the sugar deoxyribose
RNA is a polymer of nucleotides A, C, G, and U with the sugar ribose

Nucleotides

Nucleotides can be either purines (A and G) with a double ring base or pyrimidines (C, T, and U) with a single ring base

Watson-Crick Model of DNA

Double helix with sugar-phosphate backbone outside
Antiparallel strands
Strict base-pairing of nucleotides (A:T; C:G)
Two strands held together by hydrogen bonding between bases

DNA Replication

Semi-conservative replication: each parental strand is used as a template to make a daughter strand along its entire length
Results in two double helices, each with an “old” DNA strand paired with a “new” DNA strand

Proteins Involved in DNA Replication

Helicase: breaks hydrogen bonds between bases
Topoisomerase: relieves strain caused by helicase (overwound DNA)
Single Strand Binding Protein: prevents DNA strands from winding back together
Primase: makes an RNA primer
DNA polymerase III: extends the 3' end of the primer to make a new DNA strand
DNA pol I: removes the RNA primer and replaces it with DNA nucleotides
Ligase: links two DNA fragments together with a covalent bond

DNA Replication Process

Starts at an origin of replication, where origin recognition proteins bind and separate the DNA strands
A replication bubble consists of two replication forks that move away from each other in opposite directions
Helicase breaks hydrogen bonds between nucleotides at the fork, making the bubble bigger and exposing new single-stranded DNA
Topoisomerase relieves strain created by helicase by cutting and repairing the double helix
Primase makes a short RNA primer to provide a pre-existing 3'-end
DNA polymerase III extends each primer by adding DNA nucleotides to the 3'-end
DNA polymerase I removes the RNA primer and replaces it with DNA nucleotides
Ligase adds a phosphodiester bond between the 3'- and 5'-ends of two fragments, making a single daughter strand

Leading and Lagging Strands

On the leading strand, the 3'-end of the daughter DNA is towards the fork, so DNA polymerase III follows helicase and makes one long daughter strand
On the lagging strand, the 3'-end of the daughter DNA is away from the fork, so DNA polymerase III goes the "wrong way" and creates DNA fragments

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Description

Test your understanding of the molecular structure of DNA and RNA, including the composition of nucleotides, sugar molecules, and the Watson-Crick Model of DNA. Learn about the differences between purines and pyrimidines, and how they come together to form these essential biomolecules.