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ESA1 - Molecules, Genes And Disease > Transcription And Translation > Flashcards

Transcription And Translation Flashcards

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1
Q

What is the difference between the expression of genes in chromatin?

A
  • EUCHROMATIN genes are expressed

- HETEROCHROMATIN genes are not expressed

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2
Q

What are the 3 stages of both transcription and translation?

A
  • INITIATION
  • ELONGATION
  • TERMINATION
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3
Q

What is the promotor sequence commonly found in eukaryotes?

A
  • TATA box

TATAAAA
ATATTTT

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4
Q

What is the role of the promotor region?

A

Signals where transcription factor binds, therefore the initiation of transcription

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5
Q

What is the role of transcription factors?

A
  • Binding of transcription factor determines DIRECTION of transcription of gene (5’ to 3’)
  • Determines where RNA polymerase will bind
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6
Q

What is the difference between upstream and downstream?

A
  • UPSTREAM is in the 3’ to 5’ direction (right to left)

- DOWNSTREAM is in the 5’ to 3’ direction (left to right)

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7
Q

What does a mutation at -10 indicate?

A

Mutation is 10 bases upstream of the transcription initiation site

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8
Q

Where is the promotor sequence (TATA) located?

A

-30 upstream of the transcription initiation site

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9
Q

In which direction is mRNA synthesised?

A

5’ to 3’

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10
Q

Which strand is used as the template strand for mRNA?

A

3’ to 5’ bottom strand, so mRNA synthesised is a copy of the 5’ to 3’ coding strand

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11
Q

What is the enzyme responsible for the synthesis of mRNA?

A

RNA polymerase

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12
Q

What is the ORF?

A

Open reading frame of mRNA

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13
Q

What processing is required to transform pre mRNA to mature mRNA?

A
  • 5’ Capping
  • 3’ Polyadenylation
  • Splicing of introns
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14
Q

Describe the process of 5’ capping

A

Addition of a methylated guanine to the 5’ end of the mRNA forming a 5’-5’ link

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15
Q

What is the role of 5’ capping?

A
  • PROTECTS mRNA FROM DEGRADATION

- Recognised by translation initiation factors which allows subsequent binding of the 40s subunit to the mRNA strand

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16
Q

How is transcription terminated?

A

Transcription termination site sequence is recognised by SPECIFIC ENDONUCLEASE which cuts the chain a few bases downstream

17
Q

What enzyme is used for the addition of a 3’ polyA tail?

A

PolyA polymerase

18
Q

Describe how splicing occurs

A
  • Removal of introns from pre mRNA using a SPLICOSOME
  • HIGHLY SEQUENCE DEPENDANT
  • Remaining exons are joined together using a ligase enzyme
19
Q

What are the consequences of a mutation in an intron splice site?

A
  • Results in the skipping and removal of the adjacent exon
  • Shorter mRNA chain formed
  • Shorter protein formed
20
Q

What is UTR?

A

Untranslated regions of mRNA e,g, the 5’ cap and the 3’ polyA tail

21
Q

What are the three types of RNA?

A
  • rRNA (ribosomal)
  • mRNA (messenger)
  • tRNA (transfer)
22
Q

How can 100000+ mRNA strands be synthesised from 25000 genes?

A
  • SPLICING in eukaryotes can result in introns being left in (variable, sequence dependant)
  • Transcription initiation can happen at different regions on the promotor
23
Q

How many RNA polymerase molecules are present in eukaryotes?

A
  • e
  • RNA polymerase I (rRNA)
  • RNA polymerase II (mRNA)
  • RNA polymerase III (tRNA)
24
Q

How is translation catalysed?

A

By RIBOSOMES

25
Q

How do the structure of ribosomes differ in prokaryotes and eukaryotes?

A
  • Prokaryotes have 70s ribosomes (30s+50s)

- Eukaryotes have 80s ribosomes (60s+40s)

26
Q

What are ribosomes comprised of?

A

Many strands of rRNA and proteins

27
Q

What is the role of translation?

A

Change the laughter of the mRNA code of nucleotides into polypeptide code of amino acids

28
Q

What is a codon?

A

Triplet of bases that codes for one amino acid

29
Q

Why is the genetic code described as ambiguous and degenerate?

A
  • AMBIGUOUS as each codon only codes for one amino acid

- DEGENERATE as one amino acid Dan be coded for by multiple codons

30
Q

What is the initiation codon that begins translation?

A

AUG which codes for methionine

31
Q

What are the 3 termination (STOP) codons?

A
  • UGA
  • UAG
  • UAA
32
Q

Describe the structure of tRNA

A
  • RNA stem loop that forms a clover model

- Contains an anticodon that is specific to a codon on mRNA that codes for an amino acid

33
Q

Where does the amino acid bind on tRNA?

A

3’ end forming AMINO-ACYL tRNA

34
Q

What is the significance of the wobble position?

A
  • 5’ base of anticodon is IONISINE which can form a loose bond with the 3’ base of the codon, hence a wobble position as the tRNA is not tightly bound
  • This allows the tRNA molecule to recognise more than one codon
35
Q

What processes during translation require energy?

A
  • MULTIPLE PROCESSES REQUIRE ENERGY IN THE FORM OF GTP
  • Binding of 5’ cap binding initiation factors on 40s subunit
  • Binding of tRNA to 60s subunit
  • TRANSLOCATION of tRNA molecules from the P site to the A site
36
Q

What is the role of peptidyl transferase?

A
  • Catalyses the formation of a peptide bond between adjacent amino acids on the 3’ ends of tRNA molecules
  • TRANSFER OF THE AMINO ACID FROM THE P SITE TO THE A SITE
37
Q

What is a polysome?

A
  • mRNA chain with multiple ribosomes attachted which are translating simultaneously
  • Ribosomes attach at the 5’ and and fall off the 3’ end
38
Q

How does bacterial transcription and translation differ from humans?

A
  • Simple promotor region (Prinbow -10)
  • Different transcription factors
  • Single RNA polymerase
  • NO POST TRANSCRIPTIONAL PROCESSING
  • Smaller ribosomes (70s)
  • Coupled transcription-translation (no nucleus)
39
Q

What is a gene?

A

Section of DNA that codes for a polypeptide

ESA1 - Molecules, Genes And Disease (16 decks)

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