Nucleic Acid Structure and DNA Replication

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Questions and Answers

What role does DNA polymerase play during DNA replication?

Covalently links nucleotides to form DNA strands (correct)

Joins Okazaki fragments into a continuous strand

Removes RNA primers from the lagging strand

Synthesizes new DNA strands in a 3’ to 5’ direction

Why is the synthesis of the lagging strand considered discontinuous?

It requires multiple RNA primers that need to be synthesized independently.

It is synthesized in a 3’ to 5’ direction instead of 5’ to 3’.

It is synthesized in fragments due to the direction of movement of the replication fork. (correct)

It integrates nucleotides in a random sequence, leading to fragmentation.

What is the effect of telomeres on eukaryotic chromosomes?

They prevent erosion of genes near the ends of chromosomes. (correct)

They facilitate the shortening of chromosomes during replication.

They allow for complete replication without loss of important genes.

They are responsible for synthesizing the leading strand during replication.

How do deoxynucleoside triphosphates provide energy for nucleotide linkage?

They release pyrophosphate after breaking a phosphoanhydride bond. Signup and view all the answers

What is a potential consequence of repeated rounds of DNA replication?

Producing shorter DNA molecules due to incomplete replication of the 5’ end. Signup and view all the answers

Which nitrogenous base pairs with cytosine in DNA?

Guanine Signup and view all the answers

What role does helicase play in DNA replication?

Separates the DNA strands Signup and view all the answers

What is the primary structure of DNA composed of?

A linear polymer of nucleotides Signup and view all the answers

In what manner does DNA replication proceed from the origin of replication?

Bidirectionally from the replication bubble Signup and view all the answers

Which component is NOT part of a DNA nucleotide?

Amino acid Signup and view all the answers

Which of the following enzymes is responsible for synthesizing new DNA strands?

DNA polymerases Signup and view all the answers

What characteristic of DNA allows it to be replicated semiconservatively?

Specific base pairing between nucleotides Signup and view all the answers

Which reaction mechanism describes how daughter strands are formed during DNA replication?

Template-directed synthesis Signup and view all the answers

What structural feature of DNA helps prevent the strands from re-forming hydrogen bonds during replication?

Single-strand binding proteins Signup and view all the answers

Which of the following correctly describes the overall configuration of DNA?

A double helix of polynucleotides Signup and view all the answers

Study Notes

Nucleic Acid Structure

Nucleotides are the basic building blocks of DNA.
A DNA strand is a linear polymer, also called a polynucleotide.
The double helix structure is formed by two complementary DNA strands.
Chromosomes are DNA associated with proteins, forming a complex structure.
The genome is the complete set of genetic material in an organism.

DNA Structure

Nucleotides have three components: a phosphate group, a pentose sugar (deoxyribose), and a nitrogenous base.
Nitrogenous bases are classified as either purines (adenine, guanine) or pyrimidines (cytosine, thymine).
DNA is a linear polymer of nucleotides, a polynucleotide.
The sugar-phosphate backbone forms the structural framework of the DNA molecule.

DNA Replication

Replication begins at origins of replication, creating replication forks.
DNA replication proceeds in both directions from the origin.
Eukaryotic chromosomes have multiple origins of replication.
Replication bubbles fuse, resulting in two identical DNA molecules.

Proteins Involved in DNA Replication and Repair

Helicase unwinds the DNA double helix at the replication fork.
Primase generates RNA primers, starting points for DNA synthesis.
DNA polymerase synthesizes DNA polymers.
Topoisomerase relieves additional twisting ahead of the replication fork.
DNA ligase joins Okazaki fragments.
Single-strand binding proteins prevent the DNA strands from re-forming a double helix.
DNA polymerase links nucleotides covalently using deoxynucleoside triphosphates

Steps of DNA Replication

Step 1: Unwinding
Step 2: Initiation
Step 3: Elongation of leading and lagging strands
Step 4: Completion of lagging strand
Step 5: Proofreading

DNA Replication: Leading and Lagging Strands

Leading strand DNA is synthesized continuously, following the replication fork in the 5' to 3' direction with a single primer.
Lagging strand DNA is synthesized discontinuously in short segments called Okazaki fragments. These fragments are produced in the 5' to 3' direction, away from the replication fork. Multiple primers are necessary.
RNA primers are removed, and the Okazaki fragments are joined by DNA ligase.

Problems with Linear DNA

Linear DNA has ends that cannot be completely replicated due to the need for primers.
Repeated rounds of replication lead to shorter DNA molecules in both the lagging and leading strand.

Telomeres

Eukaryotic chromosomes have specialized nucleotide sequences called telomeres at their ends.
Telomeres protect genes from erosion during DNA replication.
Telomere shortening is associated with aging.

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Description

This quiz covers the fundamental concepts of nucleic acids, focusing on the structure of DNA, the role of nucleotides, and the process of DNA replication. Test your knowledge on nucleotide components, the double helix structure, and the mechanisms involved in DNA replication.