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Transcription and RNA Processing in Biology

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Termini in questo insieme (20)

  • What are the three main stages of transcription?

    Initiation, elongation, and termination.

  • How does RNA polymerase bind to the promoter in bacteria vs eukaryotes?

    In bacteria, RNA polymerase binds directly to the promoter DNA. In eukaryotes, transcription factors bind first and then recruit RNA polymerase II.

  • What is the role of transcription factors in eukaryotic transcription?

    They bind to the promoter DNA to help orient RNA polymerase II and form the transcription initiation complex.

  • What is the direction of RNA synthesis during elongation?

    RNA polymerase adds nucleotides to the 3' OH end of the growing RNA strand, synthesizing RNA in the 5' to 3' direction.

  • What are the conserved consensus sequences in bacterial promoters?

    The -35 and -10 sequences (Pribnow box) upstream of the transcription start site.

  • What is the TATA box and where is it found?

    A conserved DNA sequence (~25 nucleotides upstream) in eukaryotic promoters that helps position RNA polymerase II.

  • Which DNA strand serves as the template for RNA polymerase?

    The template strand is the DNA strand that is complementary and antiparallel to the RNA transcript.

  • What is the difference between the coding strand and the template strand?

    The coding strand has the same sequence as the RNA (except T instead of U), while the template strand is used by RNA polymerase to synthesize RNA.

  • What is the role of the poly(A) site in eukaryotic transcription?

    It signals transcription termination and addition of the poly(A) tail to the mRNA.

  • How is transcription terminated in bacteria?

    By formation of an mRNA hairpin structure at the termination sequence, causing RNA polymerase to detach.

  • What are cis-acting elements in transcription?

    DNA sequences on the same molecule as the gene they regulate, such as promoters and enhancers.

  • What are trans-acting factors in transcription?

    Proteins, like transcription factors, that regulate genes and can act at a distance from the gene they were transcribed from.

  • What RNA polymerases exist in eukaryotes and their functions?

    RNA Pol I: transcribes large rRNA; RNA Pol II: transcribes mRNA and snRNAs; RNA Pol III: transcribes tRNA and small rRNA.

  • How does RNA processing differ between prokaryotes and eukaryotes?

    Prokaryotes have no RNA processing; eukaryotes add a 5' cap, splice introns, add a 3' poly(A) tail, and export mRNA from the nucleus.

  • What is the function of the 5' cap on eukaryotic mRNA?

    It prevents mRNA degradation, facilitates nuclear export, and enhances translation efficiency.

  • What is the function of the 3' poly(A) tail on eukaryotic mRNA?

    It protects mRNA from degradation and aids in nuclear export and translation.

  • How do spliceosomes recognize intron sequences for splicing?

    Small nuclear RNAs (snRNAs) in the spliceosome base pair complementarily with conserved intron sequences.

  • What is the consequence of splice site mutations?

    They can cause introns to be retained, leading to premature stop codons and truncated proteins.

  • What is the direction of RNA polymerase movement relative to the promoter?

    RNA polymerase moves downstream from the promoter, synthesizing RNA 5' to 3'.

  • What determines which DNA strand is used as the template for a gene?

    The location and orientation of the promoter relative to the gene.