Molecular Biology Quiz on DNA and RNA Functions

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Questions and Answers

What is the primary function of messenger RNA (mRNA)?

  • To code for proteins by carrying genetic information from DNA to ribosomes. (correct)
  • To transport amino acids to ribosomes for protein synthesis.
  • To regulate gene expression by binding to specific DNA sequences.
  • To synthesize new DNA strands during replication.

According to Chargaff's rules, if the percentage of guanine (G) in a DNA molecule is 25%, what is the percentage of cytosine (C) in the same molecule?

  • 10%
  • 50%
  • 25% (correct)
  • 75%

How did Oswald Avery's experiments contribute to the understanding of DNA as the genetic material?

  • Avery discovered the structure of DNA, revealing its double helix shape.
  • Avery identified the base pairing rules in DNA, explaining how genetic information is encoded.
  • Avery's work showed that DNA, not protein, was responsible for transforming bacteria. (correct)
  • Avery's experiments proved that RNA, not DNA, is the primary genetic material.

Which type of RNA is responsible for bringing specific amino acids to the ribosomes during protein synthesis?

<p>transfer RNA (tRNA) (B)</p> Signup and view all the answers

What makes DNA a suitable molecule for storing and transmitting genetic information?

<p>Its ability to replicate itself accurately ensures that genetic information is passed on unchanged. (D)</p> Signup and view all the answers

What is the main function of helix destabilizing proteins (HD proteins) in DNA replication?

<p>Unwind the DNA double helix ahead of the replication fork (D)</p> Signup and view all the answers

How do HD proteins differ from DNA topoisomerases?

<p>HD proteins act only on single-stranded DNA, while topoisomerases act on double-stranded DNA. (C)</p> Signup and view all the answers

Which of these is NOT a characteristic of HD proteins?

<p>They act as enzymes to unwind DNA. (B)</p> Signup and view all the answers

Why is the separation of parental DNA strands essential for replication?

<p>To provide a template for DNA polymerase to synthesize new strands. (A)</p> Signup and view all the answers

In what way does the replication process differ between prokaryotes and eukaryotes?

<p>Prokaryotes have a single origin of replication, while eukaryotes have multiple origins. (B)</p> Signup and view all the answers

What is the primary function of the 3' to 5' exonuclease activity of DNA polymerase III?

<p>To remove mismatched nucleotides from the newly synthesized strand (A)</p> Signup and view all the answers

What is the role of the 'replication fork' in DNA replication?

<p>It is the region where the two parental DNA strands separate and unwind. (A)</p> Signup and view all the answers

What is the effect of nucleotide analogues on DNA replication?

<p>They block DNA chain growth, slowing down cell division (A)</p> Signup and view all the answers

Why is the replication of double-stranded DNA considered 'bidirectional'?

<p>Because replication proceeds in both directions from the origin of replication. (A)</p> Signup and view all the answers

What is the primary function of an RNA primer in DNA replication?

<p>To provide a starting point for DNA polymerase to synthesize new DNA strands. (D)</p> Signup and view all the answers

What is the significance of accurate DNA replication for an organism?

<p>All of the above. (D)</p> Signup and view all the answers

What does the term 'deleterious mutation' refer to?

<p>A change in the DNA sequence that adversely affects the organism's fitness. (D)</p> Signup and view all the answers

What happens when DNA polymerase III encounters a mismatched base during replication?

<p>It removes the mismatched base and replaces it with the correct base. (C)</p> Signup and view all the answers

What is the role of the 'HD Protein Helicase' in DNA replication?

<p>Unwinding the DNA double helix (B)</p> Signup and view all the answers

In the process of DNA replication, why is one strand called the leading strand and the other called the lagging strand?

<p>The leading strand is synthesized continuously, while the lagging strand is synthesized in fragments (Okazaki fragments). (A)</p> Signup and view all the answers

Which of the following statements is TRUE about the 5' to 3' polymerase activity of DNA polymerase III?

<p>It is used to add nucleotides to the growing DNA strand. (C)</p> Signup and view all the answers

What is the primary function of the 5’→3’ exonuclease activity of DNA polymerase I?

<p>Remove nucleotides from a base paired region (D)</p> Signup and view all the answers

What catalyzes the final phosphodiester linkage in DNA synthesis?

<p>DNA ligase (B)</p> Signup and view all the answers

What activity does DNA polymerase I perform to remove RNA primers?

<p>5'→3' exonuclease activity (C)</p> Signup and view all the answers

Which DNA polymerase is known as RNA polymerase or DNA primase and lays down primers on the lagging strand?

<p>DNA polymerase α (A)</p> Signup and view all the answers

Which of the following is a role of DNA polymerase β?

<p>Editing and repair of DNA (C)</p> Signup and view all the answers

Which function is specifically attributed to the 3'→5' exonuclease activity of DNA polymerase?

<p>Degrading improperly base paired nucleotides (B), Proofreading the newly synthesized DNA (D)</p> Signup and view all the answers

What provides energy for the joining of DNA strands in humans during replication?

<p>Cleavage of ATP to AMP and PPi (D)</p> Signup and view all the answers

What role does DNA polymerase III play in DNA synthesis?

<p>It synthesizes DNA until blocked by RNA primers. (B)</p> Signup and view all the answers

What is the key difference between the 5’→3’ and 3’→5’ exonuclease activities of DNA polymerases?

<p>5’→3’ exonuclease removes one nucleotide at a time (B)</p> Signup and view all the answers

How does DNA polymerase I locate the gap between newly synthesized DNA and RNA primer?

<p>Locating the nick between DNA and RNA (A)</p> Signup and view all the answers

Which DNA polymerase is unique to mitochondria?

<p>DNA polymerase Υ (B)</p> Signup and view all the answers

What direction does DNA polymerase I move to remove RNA nucleotides?

<p>5'→3' (B)</p> Signup and view all the answers

What type of activity does DNA polymerase I have in addition to 5'→3' polymerase activity?

<p>5'→3' exonuclease activity (C)</p> Signup and view all the answers

What process continues until RNA is totally degraded during DNA replication?

<p>DNA proofreading and synthesis (B)</p> Signup and view all the answers

What does the proofreading function of DNA polymerase involve?

<p>Detection of incorrect base pairs (D)</p> Signup and view all the answers

What initially blocks DNA polymerase III from synthesizing DNA?

<p>A stretch of RNA primer (B)</p> Signup and view all the answers

What is the main difference between the leading strand and lagging strand during DNA synthesis?

<p>The leading strand is synthesized continuously, while the lagging strand is synthesized in fragments. (C)</p> Signup and view all the answers

What role does the primer play in DNA synthesis?

<p>It provides the necessary initiator sequence for DNA polymerase. (A)</p> Signup and view all the answers

Which enzyme is primarily responsible for catalyzing DNA chain elongation?

<p>DNA polymerase III (C)</p> Signup and view all the answers

In which direction does the new DNA strand grow during synthesis?

<p>5'→3' (C)</p> Signup and view all the answers

What is required for DNA polymerases to initiate synthesis?

<p>A short double-stranded region with a free OH group (A)</p> Signup and view all the answers

What are Okazaki fragments?

<p>Discontinuous segments of DNA synthesized on the lagging strand. (A)</p> Signup and view all the answers

Which of the following deoxyribonucleoside triphosphates are NOT required for DNA synthesis?

<p>ATP (D)</p> Signup and view all the answers

How does the nucleotide building block of DNA exist?

<p>As deoxyribonucleoside triphosphates. (C)</p> Signup and view all the answers

Flashcards

Exonuclease Activity

The process of removing nucleotides from DNA ends, either 5'→3' or 3'→5'.

5'→3' Exonuclease

Exonuclease activity that removes nucleotides from the 5' end of DNA.

3'→5' Exonuclease

Exonuclease activity that removes nucleotides from the 3' end of DNA.

DNA Polymerase I

Enzyme with exonuclease activity that repairs DNA and removes RNA primers.

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DNA Polymerase III

Main enzyme in DNA replication for synthesizing new DNA strands.

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DNA Ligase

Enzyme that connects DNA strands by forming phosphodiester bonds.

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ATP Cleavage

Process providing energy required for DNA ligation, breaking ATP into AMP and PPi.

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DNA Polymerases in Eukaryotes

Group of at least 15 DNA polymerases each with unique functions in DNA processes.

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Leading strand

The continuous strand of DNA synthesized during DNA replication.

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Lagging strand

The discontinuous strand of DNA synthesized in short segments during DNA replication.

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5'→3' polymerase activity

The activity where DNA polymerase adds nucleotides in a 5' to 3' direction during replication.

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3'→5' exonuclease activity

The proofreading function of DNA polymerase that removes incorrectly paired nucleotides.

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Replication fidelity

The accuracy of DNA replication, ensuring that the nucleotide sequence is copied correctly.

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Nucleotide analogues

Modified nucleotides that can block DNA replication and slow cell division.

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Hydrolytic removal

The process by which DNA polymerase III removes incorrectly inserted nucleotides during replication.

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Okazaki Fragments

Short DNA fragments synthesized on the lagging strand during replication.

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RNA Primer

Short RNA sequence that provides a starting point for DNA synthesis.

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3' OH Group

The end of a DNA or RNA strand that provides a site for nucleotide addition.

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DNA Chain Elongation

Process of adding nucleotides to the growing DNA strand, catalyzed by DNA polymerase.

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Anti-Parallel Strands

DNA strands that run in opposite directions, essential for replication.

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Strand Separation

The process where DNA strands separate for replication.

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Replication Fork

The Y-shaped region where DNA strands unwind during replication.

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Helix Destabilizing Proteins (HD Proteins)

Proteins that keep the DNA strands separated during replication.

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Single-Stranded DNA Binding Proteins (SSB)

Proteins that bind to and stabilize single-stranded DNA.

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Replication Origin (Ori)

The starting point for DNA replication in prokaryotes.

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Structure of DNA

DNA is a double-helix made of nucleotides, consisting of a sugar, phosphate group, and nitrogenous base.

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Chargaff's Rules

  1. Percent guanine equals percent cytosine. 2) Percent thymine equals percent adenine. DNA composition varies by species.
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Types of RNA

RNA types include mRNA (carries codes), rRNA (part of ribosomes), and tRNA (transfers amino acids).

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Photo 51

An X-ray diffraction image crucial for understanding DNA structure, taken by Rosalind Franklin.

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RNA Polymerase

An enzyme that synthesizes RNA from a DNA template, important for transcription.

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Nick

The space between the 3' end of newly synthesized DNA and the 5' end of the RNA primer.

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Study Notes

DNA and RNA Structure

  • DNA is a double helix with two antiparallel strands
  • The strands are held together by hydrogen bonds between complementary base pairs (A-T, G-C)
  • Distance between base pairs is 0.34 nm
  • DNA has a sugar-phosphate backbone
  • RNA is a single-stranded molecule
  • RNA has a different sugar (ribose) than DNA (deoxyribose)
  • RNA contains uracil (U) instead of thymine (T)
  • Different types of RNA include mRNA, tRNA, and rRNA

Erwin Chargaff's Rules

  • Chargaff's rules describe the base composition of DNA
  • Rule 1: The amount of guanine equals the amount of cytosine, and the amount of adenine equals the amount of thymine
  • Rule 2: The base composition of DNA varies between species

Photo 51

  • Photo 51 is an X-ray diffraction image of DNA
  • It was taken by Rosalind Franklin and a student.

Oswald Avery

  • Oswald Avery's work was significant in demonstrating DNA's role as the transforming molecule.
  • He experimented on bacterial extracts to determine how traits are passed down.

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