Modification of mRNA Flashcards

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1
Q

What does the modification of mRNA mean? 3

A
  • mRNA strand can produce more than 1 amino acid sequence
  • Alternative mRNA strands are translated into proteins with slightly different primary and tertiary structures
  • So one gene can code for more than one protein
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2
Q

What does the DNA sequence contain?

A
  • Introns

- Exons

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3
Q

What are introns?

A

Sections of DNA that do not code for amino acids

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4
Q

What are exons?

A

Sections of DNA that do code for amino acids

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5
Q

List the stages from DNA strand to completed mRNA strand 3

A
  • Transcription
  • Splicing
  • Alternative splicing
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6
Q

What is formed from transcription of mRNA?

A

Pre-mRNA

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7
Q

What is pre-mRNA?

A

mRNA strand containing both exons and introns

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8
Q

What occurs in splicing?

A

Introns removed and exons joined

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9
Q

What occurs in alternative splicing?

A

Removes certain exons to form different mRNA strands from the same gene with different combinations of exons

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10
Q

Does modification of mRNA occur in prokaryotes?

A

No - no introns/splicing in prokaryotes

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11
Q

How is mRNA modified in antibodies? 2

A
  • Two exons in the gene for an antibody heavy chain code for anchoring an antibody to the B cell membrane
  • For a secreted antibody these are removed from pre-mRNA
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12
Q

How is a molecule of mRNA produced? 5

A
  • DNA unzips and one strand acts as a template
  • Ribonucleotides pair up with complementary bases
  • RNA polymerase joins ribonucleotides together to form pre-mRNA
  • The mRNA has fewer bases than pre-mRNA
  • As a result of removal of introns so it is made up of exons only
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13
Q

How can mRNA formation account for more proteins than there are genes? 5

A
  • It was assumed that one gene makes one protein
  • One gene can make more than one mRNA
  • One gene can code for several proteins
  • Due to removal of different exons
  • Post transcriptional change
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14
Q

What are splicing and alternative splicing?

A

Post transcriptional changes

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