Molecular Biology: DNA Replication Quiz

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Questions and Answers

What is the main function of RNA primase during DNA replication?

To extend the new DNA strands

To remove DNA primers and replace them with DNA

To join Okazaki fragments

To lay down an RNA primer for DNA polymerase (correct)

What differentiates the template for the leading strand from the lagging strand during DNA replication?

The leading strand is synthesized discontinuously, while the lagging strand is continuous.

The leading strand is read continuously in a 3' to 5' direction, while the lagging strand is read in the same direction, but discontinuously. (correct)

The leading strand synthesizes Okazaki fragments, unlike the lagging strand.

The leading strand requires multiple primers, unlike the lagging strand.

What role does DNA ligase play in the process of DNA replication?

It removes RNA primers and replaces them with DNA.

It joins nicks between DNA fragments. (correct)

It acts as a template for DNA polymerase.

It synthesizes Okazaki fragments.

What characteristic is notable about telomeres in eukaryotic chromosomes?

They protect chromosomes from unraveling and buffer against loss of replication. Signup and view all the answers

Which of the following statements about DNA polymerase I and III is correct?

DNA polymerase I removes RNA primers, while DNA polymerase III extends the new DNA strands. Signup and view all the answers

What is the correct model of DNA replication that was concluded by Meselson and Stahl?

Semiconservative model Signup and view all the answers

Which enzyme is responsible for linking new nucleotides during DNA replication?

DNA polymerase Signup and view all the answers

Which of the following statements about the structure of DNA is incorrect?

A binds with C and T with G. Signup and view all the answers

During DNA replication, in which direction does the new strand grow?

5' to 3' Signup and view all the answers

What is released during the nucleotide linkage process in DNA replication?

Pyrophosphate Signup and view all the answers

What role do regulatory proteins play in DNA structure?

They determine whether a gene is active or inactive. Signup and view all the answers

What is the function of DNA helicase during DNA replication?

To separate the two DNA strands. Signup and view all the answers

Which part of the nucleotide acts as the energy source during DNA replication?

Phosphoanhydride bonds Signup and view all the answers

What was the main conclusion from Frederick Griffith's experiments regarding the genetic material?

DNA is the transforming factor. Signup and view all the answers

Which strain of Streptococcus pneumoniae has a protective capsule?

S strain Signup and view all the answers

What was the purpose of Avery et al.'s experiment in 1944?

To identify whether DNA or protein was the transforming factor. Signup and view all the answers

In Griffith's experiment, what was observed after R cells took up genetic material from dead S cells?

R cells became virulent. Signup and view all the answers

What does the term 'transforming factor' refer to in the context of Griffith's experiments?

The DNA taken in by R cells from dead S cells. Signup and view all the answers

Why are telomeres important in DNA replication?

They prevent the loss of important genetic information during replication. Signup and view all the answers

What role does DNA proofreading play in genetic fidelity?

It checks and corrects errors during DNA replication. Signup and view all the answers

What is the primary purpose of DNA packaging in cells?

To fit long DNA molecules into the cell nucleus. Signup and view all the answers

What causes telomere shortening during DNA replication?

Non-replicated 3' ends of the lagging strand Signup and view all the answers

What is a key characteristic of Werner syndrome?

It is caused by a mutation in the WRN protein. Signup and view all the answers

What was the main purpose of the Hershey-Chase experiment?

To identify whether DNA or protein is the genetic material Signup and view all the answers

Which mechanism helps correct DNA replication errors as they occur?

Proofreading mechanism of polymerase Signup and view all the answers

How does mismatch repair identify incorrect bases in DNA?

By detecting non-methylated incorrect bases Signup and view all the answers

What conclusion resulted from the Hershey-Chase experiment regarding phage T2?

DNA, not protein, is the genetic material of phage T2 Signup and view all the answers

According to Chargaff's rules, which nucleotide pairs occur in a 1:1 ratio?

A with T and C with G Signup and view all the answers

What is the typical mutation rate in E. coli nucleotides?

1 in 10^9 nucleotides Signup and view all the answers

What are the four primary functions of DNA mentioned in the content?

Store info, replicate, express phenotype, and undergo mutations Signup and view all the answers

What role does oxidative stress play in aging?

It causes damage to cellular DNA. Signup and view all the answers

What is the primary function of telomerase in cells?

To elongate telomeres Signup and view all the answers

What structural discovery about DNA was made by Watson and Crick in 1953?

DNA is a double helix Signup and view all the answers

Which of the following best describes the end replication problem?

Incomplete replication of the 3' ends of the lagging strand Signup and view all the answers

What aspect of DNA contributes directly to its function in evolution?

The sequence of nucleotides Signup and view all the answers

What role did Rosalind Franklin play in the discovery of DNA's structure?

Her X-ray crystallography provided key insights Signup and view all the answers

Which of the following statements about the components of DNA is accurate prior to 1950?

Nucleotides are made of sugar, phosphate, and a nucleotide base Signup and view all the answers

Study Notes

DNA Structure and Replication

DNA is the genetic material of life.
DNA has a double helix structure.
DNA replication is a process where DNA makes a copy of itself.
DNA proofreading and repair mechanisms correct errors in replication and environmental damage.
Telomeres are the ends of eukaryotic chromosomes protecting them from loss of information.
Telomeres are rich in TTAGGG sequence (in humans).
Telomere shortening is an aging problem

DNA as Genetic Material

1928, Frederick Griffith experimented with Streptococcus pneumoniae bacteria.
He used S (smooth) and R (rough) strains to show transformation.
This indicated that genetic material was transferred, possibly DNA.

Identifying the Transforming Substance

1944, Avery et al. identified DNA as the transforming substance.
1952, Hershey and Chase used bacteriophages to confirm DNA as genetic material.
They labeled phage DNA and proteins radioactively and traced DNA entry into bacterial cells.

DNA Structure

DNA is a double helix.
1 turn is 3.4 nm.
Distance between adjacent nucleotides = 0.34 nm.
The structure suggests a replication method.
A pairs with T and C pairs with G.
DNA is a double helix with an antiparallel and right-handed orientation.

DNA Replication

The basic idea: one strand acts as a template for making a new strand.
Four requirements: template, complementary base-pairing, building blocks (dNTPs), and an enzyme (DNA polymerase).
DNA polymerase needs energy (phosphoanhydride bonds of dNTPs).
Three major steps of replication include denaturation, primer linking to start new strands and strand elongation (forming new strands).

Semiconservative Replication (Correct model)

Meselson and Stahl study used density gradient centrifugation to separate DNA based on 14N and 15N isotopes.
Their results supported the semiconservative model of replication.

DNA Proofreading and Repair

DNA is subject to errors of replication and environmental damage.
Replication is very fast in E. coli (1000 base pairs/second).
Proofreading and repair mechanism in DNA polymerase corrects errors as DNA is made .
Mismatch repair scans DNA to correct mismatches.
Excision repair removes UV or chemically damaged bases.

Packaging DNA

DNA is packaged with histone proteins.
Nucleosomes are formed (DNA wrapped around histone octamers).
10-nm fiber, 30-nm fiber and 300-nm loop domains.
Chromosomes are ultimately formed.

Telomere End Replication Problem

The 3' end of the lagging strand template is not completely replicated because DNA polymerase can only add nucleotides to the 3' end.
Okazaki fragments are formed in lagging strand replication.

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Description

Test your knowledge on the processes and enzymes involved in DNA replication! This quiz covers key concepts such as the role of RNA primase, the function of DNA ligase, and the differences between leading and lagging strands. Challenge yourself with questions on nucleotide linkage and the structure of DNA.