The enzyme that synthesizes RNA from a DNA template is

Answer: RNA polymerase RNA polymerase transcribes DNA into RNA in the 5'→3' direction.

Which best describes how RNA polymerase reads DNA during transcription?

Answer: It reads the template strand 3' to 5' and synthesizes RNA 5' to 3'. RNA polymerase reads the template (antisense) strand 3' to 5', polymerizing the new RNA in the 5' to 3' direction. Unlike DNA polymerase, RNA polymerase does not require a primer.

What roles do the 5' cap and 3' poly-A tail play in mRNA function?

Answer: They protect the mRNA from exonuclease degradation and aid in nuclear export and ribosome binding. The 7-methylguanosine cap and poly-A tail stabilize mRNA against exonucleases, facilitate nuclear export, and promote ribosome recruitment for translation.

AP Biology · Topic 6.3

Transcription and RNA Processing Practice

Part of Gene Expression and Regulation.(IST-1.K)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$The enzyme that synthesizes RNA from a DNA template is$
- A
  $DNA polymerase$
- B
  $RNA polymerase$
  check_circle
- C
  $Ribosome$
- D
  $Helicase$
Why
$RNA polymerase transcribes DNA into RNA in the 5'\to3' direction.$
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Sample 2difficulty 1/5
$The diagram shows a transcription bubble with RNA polymerase synthesizing a nascent RNA from a DNA template.$
$Which best describes how RNA polymerase reads DNA during transcription?$
- A
  $It reads the template strand 3' to 5' and synthesizes RNA 5' to 3'.$
  check_circle
- B
  $It requires a primer made by primase.$
- C
  $It reads both strands simultaneously.$
- D
  $It reads the template strand 5' to 3' and synthesizes RNA 3' to 5'.$
Why
$RNA polymerase reads the template (antisense) strand 3' to 5', polymerizing the new RNA in the 5' to 3' direction. Unlike DNA polymerase, RNA polymerase does not require a primer.$
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Sample 3difficulty 1/5
$What roles do the 5' cap and 3' poly-A tail play in mRNA function?$
- A
  $They protect the mRNA from exonuclease degradation and aid in nuclear export and ribosome binding.$
  check_circle
- B
  $They mark the mRNA for degradation.$
- C
  $They serve as splice donor and acceptor sites.$
- D
  $They are translated as protein extensions.$
Why
$The 7-methylguanosine cap and poly-A tail stabilize mRNA against exonucleases, facilitate nuclear export, and promote ribosome recruitment for translation.$
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Sample 4difficulty 2/5
$What is the function of the TATA box in eukaryotic promoters?$
- A
  $It encodes a small regulatory peptide.$
- B
  $It functions as the ribosome binding site (Shine-Dalgarno).$
- C
  $It catalyzes splicing of the pre-mRNA.$
- D
  $It is a binding site for general transcription factors that recruit RNA polymerase II to the transcription start site.$
  check_circle
Why
$The TATA box, located ~25 bp upstream of the start site, is bound by TBP (a subunit of TFIID); this assembles the preinitiation complex and positions RNA polymerase II for transcription initiation.$
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Sample 5difficulty 2/5
$A promoter is$
- A
  $A regulatory region where repressors bind to silence transcription$
- B
  $A DNA sequence where RNA polymerase binds and initiates transcription$
  check_circle
- C
  $An RNA sequence where ribosomes bind and initiate translation$
- D
  $A protein complex that recruits DNA polymerase to origins of replication$
Why
$Promoters are upstream of the gene; in eukaryotes the TATA box is a common element in core promoters.$
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