Untitled Quiz

Questions and Answers

In the accompanying image, a nucleotide is indicated by the letter _____

Which of these is a difference between a DNA and an RNA molecule?

DNA is usually double-stranded, whereas RNA is usually single-stranded

This is an image of a(n) _____

nucleotide

The letter A indicates a _____

phosphate group Signup and view all the answers

A nitrogenous base is indicated by the letter _____

C Signup and view all the answers

You can tell that this is an image of a DNA nucleotide and not an RNA nucleotide because you see a _____

sugar with two, and not three, oxygen atoms Signup and view all the answers

Which of these nitrogenous bases is found in DNA but not in RNA?

thymine Signup and view all the answers

Which of these is(are) pyrimidines?

C, D, and E Signup and view all the answers

In a nucleotide, the nitrogenous base is attached to the sugar's _ carbon and the phosphate group is attached to the sugar's _ carbon.

1'... 5' Signup and view all the answers

Nucleic acids are assembled in the _____ direction.

5' to 3' Signup and view all the answers

In a DNA double helix an adenine of one strand always pairs with a(n) _ of the complementary strand, and a guanine of one strand always pairs with a(n) _ of the complementary strand.

thymine...cytosine Signup and view all the answers

This is an image of a _____.

phage Signup and view all the answers

Who demonstrated that DNA is the genetic material of the T2 phage?

Hershey and Chase Signup and view all the answers

The radioactive isotope 32P labels the T2 phage's _____

DNA Signup and view all the answers

Hershey and Chase used _____ to radioactively label the T2 phage's proteins.

35S Signup and view all the answers

After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found that they contained _, which demonstrated that _ is the phage's genetic material.

labeled DNA...DNA Signup and view all the answers

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8% Signup and view all the answers

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information. Which of the following characteristics of DNA is responsible for this?

sequence of bases Signup and view all the answers

For a science fair project, two students decided to repeat the Hershey and Chase experiment with modifications. They decided to radioactively label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins. Signup and view all the answers

DNA replication is said to be semiconservative. What does this mean?

Each new double helix consists of one old and one new strand. Signup and view all the answers

What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?

telomeres Signup and view all the answers

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

No replication fork will be formed. Signup and view all the answers

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?

It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. Signup and view all the answers

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?

5' A C G U U A G G 3' Signup and view all the answers

Why does a new DNA strand elongate only in the 5' to 3' direction during DNA replication?

DNA polymerase can add nucleotides only to the free 3' end. Signup and view all the answers

Which of the following types of molecules help to hold the DNA strands apart while they are being replicated?

single-strand DNA binding proteins Signup and view all the answers

Semiconservative replication involves a template. What is the template?

one strand of the DNA molecule Signup and view all the answers

Which of the following statements accurately describes the structure of a eukaryotic chromosome?

It is a single linear molecule of double-stranded DNA plus proteins Signup and view all the answers

If a cell were unable to produce histone proteins, which of the following results would be a likely effect on the cell?

The cell's DNA could not be packed into its nucleus. Signup and view all the answers

During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?

DNA synthesis can take place only in the 5' to 3' direction. Signup and view all the answers

Short segments of newly synthesized DNA are joined into a continuous strand by _____.

ligase Signup and view all the answers

After DNA replication is completed, _____

each new DNA double helix consists of one old DNA strand and one new DNA strand Signup and view all the answers

The action of helicase creates _____.

replication forks and replication bubbles Signup and view all the answers

Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?

DNA polymerase can assemble DNA only in the 5' to 3' direction. Signup and view all the answers

An old DNA strand is used as a _____ for the assembly of a new DNA strand.

template Signup and view all the answers

What catalyzes DNA synthesis?

DNA polymerase Signup and view all the answers

Which of the following statements about DNA synthesis is true?

Primers are short sequences that allow the initiation of DNA synthesis. Signup and view all the answers

Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?

Phosphate groups Signup and view all the answers

Which of the following enzymes creates a primer for DNA polymerase?

Primase Signup and view all the answers

Which of the following statements about Okazaki fragments in E. coli is true?

They are formed on the lagging strand of DNA. Signup and view all the answers

Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?

Topoisomerase Signup and view all the answers

True or false? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but oriented in opposite directions.

True Signup and view all the answers

Study Notes

Nucleotides and Nucleic Acids

Nucleotides consist of a phosphate group, a nitrogenous base, and a sugar.
In RNA, the sugar has three oxygen atoms, while in DNA it has two.
DNA is typically double-stranded, while RNA usually exists as a single strand.
Nitrogenous bases in DNA include adenine, thymine, cytosine, and guanine; thymine is exclusive to DNA.
Pyrimidines include cytosine, thymine, and uracil, differentiating these from purines like adenine and guanine.

DNA Structure and Function

DNA strands are oriented in an antiparallel manner, with the nitrogenous base attached to the sugar's 1' carbon, and the phosphate on the 5' carbon.
DNA is synthesized in the 5' to 3' direction due to the function of DNA polymerase.
The sequence of nitrogenous bases in DNA encodes extensive hereditary information.

DNA Replication

DNA replication is semiconservative; each new DNA double helix comprises one old strand and one new strand.
Leading strands are synthesized continuously, while lagging strands are formed in short fragments known as Okazaki fragments.
Telomeres protect the ends of chromosomes but shorten with each replication; telomerase lengthens these.
Helicase unwinds DNA, creating replication forks, and topoisomerase relieves supercoiling tension.

Experimental Evidence

Hershey and Chase demonstrated DNA as the genetic material in the T2 phage, using radioactive isotopes to label DNA and proteins.
A primer forms at specific nucleotides to initiate DNA synthesis, created by primase.
Nucleic acid synthesis requires energy, provided by the phosphate groups in deoxynucleoside triphosphates (dNTPs).

Implications of Mutations and Enzyme Functions

Mutations in genes such as dnaB can prevent replication fork formation, halting DNA replication.
Single-strand binding proteins help stabilize unwound DNA strands during replication.
Mutations preventing histone production would hinder DNA packaging into nucleosomes, affecting cellular structure.

Summary of Key Enzymes

DNA polymerase is crucial for DNA synthesis and requires primers to initiate.
Ligase joins Okazaki fragments into continuous DNA strands post-replication.
Primase synthesizes short RNA primers for DNA polymerase to extend.

General Concepts

The abundance of cytosine in DNA relates to the percentage of thymine found, following Chargaff's rules.
Understanding the role of each enzyme and molecular component is essential in molecular biology, particularly for DNA replication and repair mechanisms.

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Untitled Quiz

Questions and Answers

In the accompanying image, a nucleotide is indicated by the letter _____

Which of these is a difference between a DNA and an RNA molecule?

This is an image of a(n) _____

The letter A indicates a _____

A nitrogenous base is indicated by the letter _____

You can tell that this is an image of a DNA nucleotide and not an RNA nucleotide because you see a _____

Which of these nitrogenous bases is found in DNA but not in RNA?

Which of these is(are) pyrimidines?

In a nucleotide, the nitrogenous base is attached to the sugar's _____ carbon and the phosphate group is attached to the sugar's _____ carbon.

Nucleic acids are assembled in the _____ direction.

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.

This is an image of a _____.

Who demonstrated that DNA is the genetic material of the T2 phage?

The radioactive isotope 32P labels the T2 phage's _____

Hershey and Chase used _____ to radioactively label the T2 phage's proteins.

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information. Which of the following characteristics of DNA is responsible for this?

DNA replication is said to be semiconservative. What does this mean?

What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?

Why does a new DNA strand elongate only in the 5' to 3' direction during DNA replication?

Which of the following types of molecules help to hold the DNA strands apart while they are being replicated?

Semiconservative replication involves a template. What is the template?

Which of the following statements accurately describes the structure of a eukaryotic chromosome?

If a cell were unable to produce histone proteins, which of the following results would be a likely effect on the cell?

During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?

Short segments of newly synthesized DNA are joined into a continuous strand by _____.

After DNA replication is completed, _____

The action of helicase creates _____.

Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?

An old DNA strand is used as a _____ for the assembly of a new DNA strand.

What catalyzes DNA synthesis?

Which of the following statements about DNA synthesis is true?

Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?

Which of the following enzymes creates a primer for DNA polymerase?

Which of the following statements about Okazaki fragments in E. coli is true?

Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?

True or false? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but oriented in opposite directions.

Study Notes

Nucleotides and Nucleic Acids

DNA Structure and Function

DNA Replication

Experimental Evidence

Implications of Mutations and Enzyme Functions

Summary of Key Enzymes

General Concepts

Studying That Suits You

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In a nucleotide, the nitrogenous base is attached to the sugar's _ carbon and the phosphate group is attached to the sugar's _ carbon.

In a DNA double helix an adenine of one strand always pairs with a(n) _ of the complementary strand, and a guanine of one strand always pairs with a(n) _ of the complementary strand.