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Biology RNA Synthesis
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Biology RNA Synthesis

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@StableEpilogue

Questions and Answers

What is the primary difference between the sugar molecule found in RNA and DNA?

Ribose

What is the purpose of the sigma factor in prokaryotic transcription initiation?

To recruit RNA polymerase to the transcription start site

What is the primary function of heterogeneous nuclear RNA (hnRNA) in eukaryotic cells?

To undergo co-transcriptional and post-transcriptional modifications to form mRNA

What is the direction of nucleotide addition during RNA synthesis?

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

What is the key difference in the sugar molecule between DNA and RNA?

<p>RNA has ribose, while DNA has deoxyribose</p> Signup and view all the answers

What is the function of ribosomal RNA (rRNA)?

<p>To provide a structural and enzymatic component of the ribosome</p> Signup and view all the answers

What is the main difference between prokaryotic and eukaryotic transcription?

<p>Eukaryotic transcription involves additional modifications to the primary transcript, whereas prokaryotic transcription does not</p> Signup and view all the answers

What is the average rate of mRNA synthesis in prokaryotes?

<p>~50 nt/sec</p> Signup and view all the answers

What is the function of transfer RNA (tRNA)?

<p>To deliver amino acids to the ribosome</p> Signup and view all the answers

What is the purpose of the promoter region in prokaryotic transcription?

<p>To recruit RNA polymerase to the transcription start site</p> Signup and view all the answers

What is the sequence of the transcript produced during transcription?

<p>Complementary to the non-template strand of DNA</p> Signup and view all the answers

What is the term for the process of converting the primary transcript (hnRNA) to mature mRNA in eukaryotic cells?

<p>Post-transcriptional modification</p> Signup and view all the answers

What is the primary mechanism of rho-dependent transcription termination?

<p>Rho unwinds the DNA-RNA duplex using its helicase activity</p> Signup and view all the answers

What is the term for the regions of DNA that are removed during RNA processing in eukaryotic cells?

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

What is the function of RNA polymerase in prokaryotic transcription?

<p>To synthesize mRNA</p> Signup and view all the answers

Why do GC-rich sequences cause RNA polymerase to pause?

<p>Because GC-rich sequences are hard to separate due to strong hydrogen bonds</p> Signup and view all the answers

What is the base that replaces thymine in RNA?

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

What is the function of the stem-loop structure in the mRNA transcript during rho-independent transcription termination?

<p>It reduces the binding of mRNA to the DNA template</p> Signup and view all the answers

What is the term for the flow of genetic information from DNA to RNA to proteins?

<p>The central dogma of molecular biology</p> Signup and view all the answers

What type of bonds join nucleotides in RNA?

<p>Covalent phosphodiester bonds</p> Signup and view all the answers

What is the purpose of rho protein in transcription termination?

<p>To unwind the DNA-RNA duplex and release the RNA transcript</p> Signup and view all the answers

What is the significance of the grey boxes in the given DNA sequence?

<p>They represent the promoter site for RNA polymerase</p> Signup and view all the answers

What is the function of the binding between sigma factor and the -10 and -35 boxes?

<p>To position RNA polymerase at the transcription start site</p> Signup and view all the answers

What is the location of the transcription start site?

<p>Nucleotide 201</p> Signup and view all the answers

What is the name of the region between nucleotides 58 and 97?

<p>Promoter region</p> Signup and view all the answers

What is the function of the sequences underlined by the straight and wiggly lines?

<p>To initiate transcription</p> Signup and view all the answers

What are the green and blue highlighted regions?

<p>Promoter and operator regions</p> Signup and view all the answers

Approximately how long is the transcript (how many nucleotides)?

<p>700 nucleotides</p> Signup and view all the answers

Would the mRNA sequence look like the original DNA sequence?

<p>No, it would be complementary</p> Signup and view all the answers

What is the function of the sigma factor?

<p>To position RNA polymerase at the transcription start site</p> Signup and view all the answers

What is the main difference between RNA polymerase II in eukaryotes and prokaryotes?

<p>C-terminal domain</p> Signup and view all the answers

Which of the following statements is NOT true about eukaryotic transcription?

<p>RNA polymerase II synthesizes mRNA in the 5' to 3' direction</p> Signup and view all the answers

What is the purpose of the spliceosome in eukaryotic cells?

<p>To remove introns from pre-mRNA</p> Signup and view all the answers

Which of the following processes occurs in the nucleus?

<p>Transcription in eukaryotes</p> Signup and view all the answers

What is the term for the regions of DNA that are removed during RNA processing in eukaryotic cells?

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

What is the purpose of co-transcriptional/post-transcriptional modifications in eukaryotic cells?

<p>To convert the primary transcript to mature mRNA</p> Signup and view all the answers

Study Notes

Transcription and RNA Synthesis

  • RNA differs from DNA in three key ways:
    • RNA is single-stranded
    • RNA contains ribose instead of deoxyribose
    • RNA contains uracil instead of thymine

Types of RNA

  • Messenger RNA (mRNA) encodes proteins
  • Ribosomal RNA (rRNA) is a structural and enzymatic component of the ribosome
  • Transfer RNA (tRNA) delivers amino acids to the ribosome

Transcription

  • The production of messenger RNA from a DNA template
  • RNA polymerase polymerizes ribonucleoside triphosphates into RNA
  • The mechanism of transcription has three parts:
    • Initiation
    • Elongation
    • Termination

Transcription in Prokaryotes

  • Initiation:
    • Short recognition sequences (‘boxes’) in the promoter region serve to align RNA polymerase at the transcription start site
    • Sigma factor binds to the -10 (Pribnow) and -35 boxes, and recruits RNA polymerase to the transcription start site
  • Elongation:
    • RNA polymerase unwinds DNA as it moves
    • RNA polymerase reads the DNA template, synthesizing mRNA by adding complementary nucleotides
    • After the first few nucleotides are complete, the sigma factor dissociates
    • Average rate of synthesis = ~50 nt/sec
    • mRNA has the same sequence as the non-template (coding) strand of DNA
  • Termination:
    • Most common method of transcription termination in E. coli
    • Termination of transcription controlled by GC-rich stop sequences in DNA
    • mRNA transcript forms a stem loop, reducing binding of mRNA to DNA template
    • String of weak A-U pairings help detachment from DNA template

Transcription in Eukaryotes

  • Key differences from prokaryotic transcription:
    • Existence of a nucleus, where transcription occurs
    • Presence of multiple RNA polymerases (I, II, and III)
    • RNA polymerase II synthesizes mRNA in the 5' to 3' direction
    • Co-transcriptional and post-transcriptional modifications occur in eukaryotic cells
  • Co-transcriptional and post-transcriptional modifications:
    • Addition of a 5' cap to eukaryotic pre-mRNA
    • Addition of a polyA tail to eukaryotic pre-mRNA
    • Splicing, which is the removal of introns from pre-mRNA
    • Export of processed mRNA into the cytoplasm

Exons and Introns

  • Exons: regions of the primary transcript that are retained in the mature mRNA
  • Introns: regions of the primary transcript that are removed during splicing

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Learn about the differences between RNA and DNA, types of RNA, and the process of transcription in this biology quiz.

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