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FLC > RNA Synthesis > Flashcards

RNA Synthesis Flashcards

1
Q

What is produced during transcription?

A

DNA -> mRNA

nucleic acid -> nucleic acid

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2
Q

Where does transcription occur?

A

Nucleus

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3
Q

What is produced during translation?

A

mRNA -> Protein

nucleic acid -> protein

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4
Q

Where does translation occur?

A

In the cytoplasm

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5
Q

What are genes made of?

A

DNA

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6
Q

What is the function of DNA?

A

Stores genetic information of the genotype

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7
Q

What is the central dogma theory?

A

DNA -> RNA -> Proteins

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8
Q

Describe what the human genome is

A

22 autosomes in human genome and a pair of sex chromosomes

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9
Q

What are chromosomes?

A

Vehicles to carry genes

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10
Q

What are centromeres?

A

(primary constriction)

microtubules of spindles joined at centromere to keep sister chromatids attached

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11
Q

What is a telomere?

A

Compound structure at the end of a chromosome (has double stranded ends of 6 base pair repeats

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12
Q

How do telomeres protect chromosome ends?

A

Double stranded ends prevent repair processes in cells joining up the ends to other chromosomes

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13
Q

What is the role of pseudogenes?

A

Duplicates of non functional genes

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14
Q

Where are DNA coding regions present on chromosomes?

A

Coding regions are spread along the chromosome with non coding regions between them

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15
Q

What is a gene?

A

A hereditary protein unit containing the phenotype and regulation regions

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16
Q

What are UTRs?

A

Untranslated regions - non coding mature mRNA

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17
Q

What are introns?

A

non coding RNA

18
Q

What are exons?

A

Coding RNA

19
Q

What is the promoter?

A

The region that initiates transcription

20
Q

Where is the promoter found?

A

Upstream of the transcription start site on the 5’ end

21
Q

How is transcription initiated?

A

RNA polymerase II binds to the start site on the 5’ end

22
Q

Explain in detail how transcription process occurs?

A
  1. TATA box (basal promoter) recognised by TATA binding protein
    (TBP) in TFIID
  2. TFIIA and TFIIB bind
    • TFIIA stabilises the compound
  3. Other general TF bind
  4. RNA Polymerase II assembles at the promoter region forming
    transcription initiation complex
  5. TFIIH (helicase) pulls apart DNA and phosphorylates RNA
    polymerase II
    6 Phosphorylated RNA Polymerase II is released from complex
    and transcription begins
23
Q

What are the different Human RNA Polymerases?

A

RNA Polymerase I - Most ribosomal RNA (rRNA)
RNA Polymerase II - Protein coding, micro RNA (miRNA)
RNA Polymerase III - Transfer RNA (tRNA) and 5S rRNA

24
Q

How do polymerases synthesise RNA?

A

By using nucleotide triphosphates e.g.

- ATP, CTP, GTP, UTP

25
Q

What is the role of the Kozak sequence?

A

Enables the ribosome to know that AUG is the start codon to allow translation to begin

26
Q

How is RNA modified?

A
  • 5’ Cap
  • PolyA tail
  • Splicing
27
Q

What is 5’ capping?

A

7-methylguanosine added to triphosphate bridge on 5’ end using the enzyme methyltransferase

28
Q

Explain the role of the 5’ cap?

A

Allows the cell to recognise the mRNA is ready to be exported out of the nucleus

29
Q

How does polyadenylation occur?

A
  1. Specific endonucleases recognise the termination stop
    codon
  2. RNA cleaved off RNA Polymerase II using CPSF
  3. Polyadenylate polymerase adds 250 A’s to 3’ end
30
Q

What is the role of the polyA tail?

A

Prevents endonucleases digesting the ends of mRNA

Aids transport within the cytoplasm

31
Q

Is there any significance to the length of the polyA tail?

A

Yes, the longer the polyA tail the more stable the mRNA molecule

32
Q

What are the consequences of mRNA strands not having a 5’ cap or 3’ polyA tail?

A

The cap and the tail signal to the cell mRNA is ready to be exported
- if either are missing the mRNA remains in the cytoplasm and RNAses will digest it

33
Q

What is splicing?

A

The removal of introns and joining of exons

34
Q

How does splicing occur?

A
  1. Cleavage at 5’ splice site
  2. Intron moves allowing GU sequence to link at Branch A
  3. Lariat forms
  4. AG at 3’ end cleaved
  5. Causes ligation of exons
  6. Introns degraded
35
Q

How is this process regulated?

A

Enzymatically controlled by spliceosomes snRNPs

36
Q

What are SnRNPs?

A

Small nuclear ribonucleic proteins

37
Q

How do SnRNPs work?

A

Bind to both sides of mRNA strand and push out the introns

38
Q

How are multiple proteins with varying functions produced from the same mRNA strand?

A

Alternative splicing results in differing proteins forming.

Different exons are chosen

39
Q

What further regulations are in place before exporting from the nucleus?

A

CBC - cap binding complex
binds to the capped molecules

EJC - exon junction complex
binds to a successfully spliced junction

40
Q

How is export from the nucleus regulated?

A

Modifications are recognised allowing mRNA molecule to be released

41
Q

Where does the mRNA leave the nucleus from?

A

Through the nuclear pore complex

FLC (34 decks)

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