Transcription and Slicing Flashcards

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1
Q

Describe how mRNA is produced from an exposed template strand of DNA (do not include DNA helicase or splicing in your answer)

A
  • Free RNA nucleotides form complementary base pairs;
  • Phosphodiester bonds form;
  • By (action of) RNA polymerase;
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2
Q

How is the structure of pre-mRNA different to mRNA?

A
  • mRNA fewer nucleotides/pre-mRNA has introns and exons
  • because of slicing
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3
Q

What is the first step of transcription?

A

(DNA helicase) causes hydrogen bonds between complementary base pairs to break in a specific region of DNA causing the strand to separate and expose the nucleotide bases

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4
Q

After they have separated, what does the single-strand of DNA act as?

A

template strand

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5
Q

What is the role of RNA polymerase?

A

to catalyse the reaction forming phosphodiester bonds between adjacent nucleotides, helping to form a pre-mRNA molecule

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6
Q

Describe how mRNA is formed by transcription in eukaryotes (7 marking points)

A
  • Hydrogen bonds (between DNA bases) break
  • one DNA strand acts as a template
  • RNA nucleotides align by complementary base pairing
  • Uracil base pairs with adenine
  • RNA polymerase joins (adjacent RNA) nucleotides
  • (By) phosphodiester bonds
  • Pre-mRNA is spliced (to form mRNA)
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7
Q

How does transcription differ in prokaryotes compared to eukaryotes?

A

In prokaryotes, transcription results directly in the production of mRNA, as prokaryotic DNA does not have introns

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8
Q

What is splicing?

A

the process which removes intons from a strand of pre-mRNA

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9
Q

How do mRNA molecules leave the nucleus?

A

through a nuclear pore (they are too large to diffuse out)

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10
Q

Where does transcription occur?

A
  • in the nucleus in eukaryotic cells
  • in the cytoplasm for prokaryotic cells
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