RNA Synthesis Flashcards

1
Q

Which is the biggest and smallest chromosome in the karyotype?

A

1= biggest and 22= smallest

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2
Q

What protects the ends of the chromosomes?

A

Telomere

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3
Q

What is the definition of a gene?

A

Unit of hereditary, or a DNA segment containing instructions for making a particular product

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4
Q

Why is the promoter region important?

A

Turns the gene on/off

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5
Q

Which of introns/Exons is expressed?

A

Exons are Expressed (remember the E’s)

Introns are spliced out

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6
Q

Where would you find an untranslated region (UTR)?

A

Part of the first and last exon

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7
Q

What is transcription? (General overview)

A

Synthesis of mRNA from DNA

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8
Q

What is translation? (General overview)

A

Nucleic acid ->protein

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9
Q

What genes do RNA polymerase 1 transcribe?

A

Most ribosomal RNA (rRNA)

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10
Q

What genes do RNA polymerase 2 transcribe?

A

Protein coding, miRNA and non coding RNA

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11
Q

What genes do RNA polymerase 3 transcribe?

A

tRNA, 5s rRNA and other small RNAs

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12
Q

How does the cell respond so quickly to changes in its environment?

A

Lots of polymerases can work simultaneously on the gene to make lots of copies of the gene

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13
Q

What molecules do you need for RNA synthesis?

A
  • DNA template
  • RNA polymerase 2
  • ribonucleotide
  • buffers
  • transcription factors
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14
Q

What is a transcription factor?

A

Proteins required to initiate or regulate transcription in eukaryotes

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15
Q

How do transcription factors work?

A
  • TATA box (promoter) recognised by the TBP subunit or TFIID
  • other transcription factors bind then RNA polymerase2 assembles at the promoter forming the transcription initiation complex
  • TFIIH (helicase) pulls apart the helix and phosphorylates RNA polymerase 2
  • phosphorylated RNA polymerase 2 is released from the complex and begins transcription
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16
Q

What does TBP stand for?

A

TATA binding protein

17
Q

Why is there a 5’ UTR?

A

Regulation of translation

18
Q

Why is there a 3’ UTR?

A

MRNA stability and miRNA binding

19
Q

What are the three steps in RNA processing?

A

Capping, polyadenylation and splicing

20
Q

What is capping and how does it work?

A

5’ end modification.

Forms a 5’-5’ triphosphate bridge and is methylated at the 7 position

21
Q

What does capping do?

A

Allows for co-transcriptional modification
can stimulate splicing
Used for the recognition of mRNA by the translation machinery in the cytoplasm of the cell

22
Q

What is polyadenylation and how does it work?

A

At some point there is a cleavage (joining) signal. Then an adenine tail is added by poly (A) polymerase

23
Q

What is the point of capping and polyadenylation?

A

Stability
Allows for the transport to the cytoplasm
And increases the integrity prior to translation

24
Q

How many introns are in one gene?

25
What is the size of an intron?
<100->700,000 nucleotides (median 1800 nucleotides)
26
How many nucleotides does an exon have on average?
123 nucleotides
27
What are the steps of splicing?
- GU and pyramiding rich region get recognised by proteins and they undergo splicing - ends join up - then the 3’ end gets cut and the two Exons join up
28
Why do introns exist?
Alternative splicing - allows you to select different Exons to make up your mature proteins Means you can make up many more proteins with less genes
29
What do you need to export the RNA from the nucleus?
Cap binding complex (CBC) Transcription-coupled export complex (TREX) Exon junction complex
30
Give some examples of where alternative splicing takes place
Alternative promoters (eg myosin) Alternative polyadenylation in ubiquitously expressed genes