DNA Structure and Replication Quiz
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Questions and Answers

How many bonds are between A and T in DNA?

2

How do we tag proteins?

Proteins are tagged with sulfur but no phosphate.

How do we tag DNA?

DNA is tagged with phosphate but no sulfur.

Is DNA replication semi-conservative or fully conservative?

<p>semi-conservative (B)</p> Signup and view all the answers

What is the significance of semi-conservative DNA replication?

<p>Semi-conservative replication ensures that each new DNA molecule inherits one parental strand, preserving genetic information.</p> Signup and view all the answers

What contributes to the high potential energy of nucleotides?

<p>Nucleotides contain three phosphate groups.</p> Signup and view all the answers

In bacteria, how many locations does DNA replication take place?

<p>1</p> Signup and view all the answers

In humans, how many locations does DNA replication take place?

<p>many</p> Signup and view all the answers

What is the role of the primer in DNA synthesis?

<p>The primer is a short RNA sequence that provides a starting point for DNA polymerase to add new nucleotides.</p> Signup and view all the answers

Give an example of a DNA sequence and its corresponding RNA primer.

<p>For the DNA sequence 3’AATTGCA5’, the corresponding RNA primer is 5’UUAACGU3’.</p> Signup and view all the answers

What is the function of DNA polymerase?

<p>DNA polymerase is an enzyme that synthesizes new DNA by adding nucleotides to an existing strand.</p> Signup and view all the answers

How does DNA polymerase ensure accuracy in DNA replication?

<p>DNA polymerase has a proofreading function that can detect and correct errors during DNA synthesis.</p> Signup and view all the answers

How does DNA polymerase recognize a mistake during DNA synthesis?

<p>If DNA polymerase incorporates an incorrect nucleotide, it creates a mismatched base pair that protrudes from the DNA helix, producing a 'bump' that is recognized by DNA polymerase.</p> Signup and view all the answers

What is the role of primase in DNA replication?

<p>Primase synthesizes short RNA primers that provide starting points for DNA polymerase.</p> Signup and view all the answers

What is the composition of the primer?

<p>The primer is made of RNA.</p> Signup and view all the answers

What is the function of DNA ligase in DNA replication?

<p>DNA ligase joins the Okazaki fragments together, creating a continuous DNA strand on the lagging strand.</p> Signup and view all the answers

What is the function of DNA helicase?

<p>DNA helicase unwinds the double-stranded DNA helix, separating the two strands to provide access for DNA polymerase.</p> Signup and view all the answers

What is the role of single-stranded DNA binding proteins (SSBPs) in DNA replication?

<p>SSBPs bind to the separated DNA strands to prevent them from re-annealing, keeping them accessible for replication.</p> Signup and view all the answers

What is the function of topoisomerase in DNA replication?

<p>Topoisomerase relieves the torsional stress caused by the unwinding of the DNA helix.</p> Signup and view all the answers

What is the replisome?

<p>The replisome is a complex of enzymes involved in DNA replication.</p> Signup and view all the answers

What is the function of the sliding clamp in DNA replication?

<p>The sliding clamp holds DNA polymerase to the DNA template, preventing it from detaching during synthesis.</p> Signup and view all the answers

What is the role of telomerase in DNA replication?

<p>Telomerase adds repetitive nucleotide sequences to the ends of chromosomes, preventing the loss of genetic information during replication.</p> Signup and view all the answers

Why does telomere length shorten with age?

<p>Telomere length shortens with age because telomerase activity declines, leading to the gradual shortening of telomeres.</p> Signup and view all the answers

How does UV damage DNA?

<p>UV radiation can cause the formation of thymine dimers, which distort the DNA structure.</p> Signup and view all the answers

What is nucleotide excision repair?

<p>Nucleotide excision repair is a process that removes damaged or incorrect nucleotides from DNA, replacing them with healthy ones.</p> Signup and view all the answers

Where does transcription (DNA to RNA) occur in eukaryotic cells?

<p>Transcription occurs in the nucleus of eukaryotic cells.</p> Signup and view all the answers

Where does translation (RNA to protein) occur?

<p>Translation occurs in the cytoplasm of cells.</p> Signup and view all the answers

How many RNA polymerases do prokaryotes have?

<p>Prokaryotes have one RNA polymerase.</p> Signup and view all the answers

What is the difference between DNA and RNA synthesis?

<p>Unlike DNA synthesis, which involves unwinding the entire DNA molecule, RNA synthesis only unwinds a small section of DNA, exposing the template strand.</p> Signup and view all the answers

What is the importance of having multiple types of RNA (mRNA, tRNA, etc.)?

<p>Different types of RNA have specialized roles in protein synthesis: mRNA carries the genetic code for protein, tRNA carries amino acids to the ribosome, and rRNA is a component of ribosomes.</p> Signup and view all the answers

Where does protein synthesis occur?

<p>Protein synthesis occurs at ribosomes.</p> Signup and view all the answers

How many bases make up a codon?

<p>A codon consists of three bases.</p> Signup and view all the answers

Why do we need three bases to make a codon?

<p>Three bases are necessary to code for 20 amino acids, considering that we have four different bases (A, T, C, G) and need a minimum of 20 codons.</p> Signup and view all the answers

What is a deletion mutation?

<p>A deletion mutation involves the removal of one or more nucleotides from a DNA sequence.</p> Signup and view all the answers

What is a point mutation?

<p>A point mutation involves a change in a single nucleotide within a DNA sequence.</p> Signup and view all the answers

What is a missense mutation?

<p>A missense mutation alters a codon, leading to a change in the amino acid sequence.</p> Signup and view all the answers

What is a frameshift mutation?

<p>A frameshift mutation shifts the reading frame of a gene, altering the sequence of amino acids from the point of mutation onward.</p> Signup and view all the answers

What is the function of the AUG codon?

<p>AUG serves as the start codon for translation, initiating the process of protein synthesis.</p> Signup and view all the answers

What is the role of the promoter and terminator in gene expression?

<p>The promoter is a DNA sequence that signals the start of transcription, while the terminator marks the end of transcription.</p> Signup and view all the answers

Why are frameshift mutations generally more detrimental than codon deletions?

<p>Frameshift mutations shift the reading frame, altering the amino acid sequence from the point of mutation onward. Codon deletions only affect the affected codon and the following amino acids.</p> Signup and view all the answers

What is the significance of the TATTA box in gene regulation?

<p>The TATTA box is located within the promoter region of genes. It is a crucial element for the binding of transcription factors. These factors initiate transcription, regulating gene expression.</p> Signup and view all the answers

What is the difference between transcription and translation in prokaryotes and eukaryotes?

<p>Transcription and translation occur simultaneously in prokaryotes, but they are separated in eukaryotes.</p> Signup and view all the answers

How does the primary transcript in a eukaryotic cell differ from a functional mature mRNA?

<p>The primary transcript contains both introns and exons. During RNA processing, introns are removed, leaving only exons in the mature mRNA.</p> Signup and view all the answers

What are the key steps in RNA processing?

<p>RNA processing involves splicing, 5' capping, and 3’ poly-A tail addition.</p> Signup and view all the answers

What is the role of the spliceosome?

<p>The spliceosome is a complex of proteins and RNA that removes introns from the primary transcript during RNA splicing.</p> Signup and view all the answers

What does tRNA do during translation?

<p>tRNA carries specific amino acids to the ribosome, matching their corresponding codons on the mRNA.</p> Signup and view all the answers

What are the three sites in the ribosome during translation?

<p>The three sites in the ribosome are the E site (exit), the P site (peptidyl), and the A site (aminoacyl).</p> Signup and view all the answers

What are the steps in the translation process?

<p>The translation process includes initiation, elongation, and termination.</p> Signup and view all the answers

What are the key post-translational modifications?

<p>Post-translational modifications include protein folding by chaperones and modifications such as phosphorylation and glycosylation.</p> Signup and view all the answers

Flashcards

A-T bond

Two hydrogen bonds

G-C bond

Three hydrogen bonds

Protein tag

Sulfur, no phosphate

DNA tag

Phosphate, no sulfur

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DNA replication

Creating new DNA using old DNA as a template

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Semi-conservative replication

Each new DNA molecule has one old and one new strand.

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DNA polymerase

Enzyme that synthesizes DNA

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Primase

Makes RNA primer for DNA polymerase

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Ligase

Glues Okazaki fragments together

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Helicase

Unwinds DNA strands

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SSBPs

Prevent separated DNA strands from re-annealing

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Topoisomerase

Relieves tension in DNA during unwinding

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Replisome

Complex of enzymes for DNA replication

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Sliding clamp

Holds DNA polymerase onto the DNA

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Telomerase

Adds nucleotides to telomeres to prevent shortening

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UV damage

Forms thymine dimers, causing DNA kinks

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Nucleotide excision repair

Fixes thymine dimers in DNA

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Transcription location

Nucleus in eukaryotes

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Translation location

Cytoplasm in eukaryotes

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RNA polymerase

Enzyme synthesizing RNA from DNA

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Prokaryotic RNA polymerase

Single type of RNA polymerase

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Eukaryotic RNA polymerase

Multiple types of RNA polymerase

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RNA synthesis

Creating RNA from one DNA strand

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Protein synthesis location

Ribosome

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Codon length

Three bases

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Study Notes

DNA Structure and Replication

  • Base Pairing: Adenine bonds with Thymine (2 bonds), Guanine with Cytosine (3 bonds).
  • DNA Tagging: Proteins are tagged with sulfur, DNA with phosphate.
  • DNA Replication: Semi-conservative, meaning each new DNA molecule has one original and one newly synthesized strand.

DNA Replication Energy

  • Endergonic Synthesis: DNA synthesis requires energy due to negatively charged phosphates repelling each other.

DNA Replication Location

  • Bacteria: Replicates in one location.
  • Humans: Replicates in multiple locations.

DNA Replication Process

  • Primer: RNA primer provides a starting point for DNA polymerase.
  • DNA Polymerase: Enzyme that assembles nucleotides, proofreads, and corrects errors (5' to 3').
  • Primase: Creates RNA primers.
  • Ligase: Glues Okazaki fragments together.
  • Helicase: Breaks hydrogen bonds between DNA strands.
  • SSBPs: Prevent separated strands from rejoining.
  • Topoisomerase: Relieves tension caused by unwinding DNA.

DNA Replication Enzymes

  • DNA Polymerase : Assembles nucleotides; proofreads.
  • Primase : Creates RNA primer.
  • Ligase : Glues Okazaki fragments.
  • Helicase : Unwinds DNA.
  • SSBPs : Stabilize single-stranded DNA.
  • Topoisomerase : Relieves DNA supercoiling.

DNA Replication Process: Leading and Lagging Strands

  • Okazaki Fragments are short DNA fragments created during replication of the lagging strand.
  • Lagging strand synthesizes discontinuously. Okazaki fragments are created, then joined to form the whole lagging strand.

Telomeres

  • Located at the ends of chromosomes
  • Shorten with age
  • Composed of repeating sequences of DNA

DNA Damage and Repair

  • UV Damage: Creates thymine dimers, causing structural kinks.
  • Nucleotide Excision Repair: Damaged nucleotides are replaced with proper ones.

Transcription and RNA

  • Location: Nucleus
  • Enzyme: RNA polymerase -RNA polymerase doesn't need a primer.

Protein Synthesis

  • Location: Ribosomes.
  • Codon length: 3 bases
  • Number of amino acids: 20
  • Codons required to code for amino acids: 64
  • Mutational Effects
  • Deletion mutation: Detrimental, no protein function
  • Addition mutation: Detrimental, no protein function
  • Point mutation: Impact varies by location

Gene Expression Differences Between Eukaryotes and Prokaryotes

  • Transcription and translation happen at the same time in prokaryotes but not in eukaryotes.

mRNA Processing in Eukaryotes

  • Introns: Non-coding regions removed from the mRNA transcript.
  • Exons: Coding regions that remain in the mRNA.
  • Processing: Splicing, 5' cap, and 3' poly-A tail are added to the mRNA.

tRNA

  • Anticodons: Complementary to mRNA codons.
  • Function: Translates mRNA codons into amino acids.
  • tRNA sites in the ribosome : E site (Exit), P site (Peptidyl-tRNA), A site (Aminoacyl-tRNA).

Translation Steps

  • Initiation: Ribosome binds to mRNA at the start codon.
  • Elongation: tRNA brings amino acids to the A site. Peptide bonds form.
  • Termination: Stop codons signal release of the ribosome from mRNA.

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Description

Test your knowledge on DNA structure and replication processes. This quiz covers key concepts including base pairing, DNA replication mechanisms, and the roles of various enzymes. Understand how DNA is replicated in different organisms and the energy requirements involved.

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