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Biology 221 > Transcription And Translation > Flashcards

Transcription And Translation Flashcards

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1
Q

Transcription

A

DNA is transcribed into an RNA copy

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2
Q

Translation

A

mRNA is translated into a polypeptide at the ribosome

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3
Q

Prokaryotic Gene Structure

A

Promoter, Regulatory Sequence, Coding Region, Terminator

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4
Q

Eukaryotic Gene Structure

A

Enhancer, Basal Promoters (CCAAT -100, TATA -25), Exons and Introns, termination

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5
Q

Basic Transcription Steps

A
  1. Initiation
  2. Elongation
  3. Termination
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6
Q

Initiation

A

Recruitment of RNA-Polymerase (also protein sigma factor for prokaryotes)
RNA polymerase separates DNA strands to form template strand

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7
Q

Elongation

A

RNA polymerase moves in a 5’-3’ direction unwinding the DNA as it goes and using template strand to synthesize the RNA.
Pyrophosphate (provides the energy for the process) is cleaved off.

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8
Q

Prokaryotic vs Eukaryotic transcription

A

Prokaryotic: All genes transcribes by the same core RNA polymerase. Direct binding by polymerase to promoter via sigma factor.

Eukaryotic: 3 polymerases used. RNA polymerases cannot bind directly to promoter but need general transcription factors.

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9
Q

RNA processing in Eukaryotes

A

RNA polymerase makes a pre-mRNA which needs to undergo processing to produce a final mature RNA.

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10
Q

RNA processing steps in Eukaryotes

A

Transcription
Capping
Splicing
Tailing

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11
Q

Capping

A

Methylguanosine cap added at 5’ end of mRNA

Limits degradation, initiate translation

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12
Q

Tailing (Polyadenylation)

A

3’ poly A tail added

Limits degradation, important for translation, required for transport out of nucleus

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13
Q

Splicing

A

Introns removed

Step 1- break 5’ phosphodiester linkage from preceding exon. Lariat loop formed
Step 2- break linkage of last nucleotide of intron from first nucleotide of the following exon. Lariat loop is maintained when broken off (eventually degrades away).

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14
Q

mRNA

A

Contains the information for the sequence of amino acids in a polypeptide according to the genetic code

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15
Q

tRNA

A

A molecule with two functional sites; the anticodon and the 3’ single stranded region where an appropriate amino acid attaches.

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16
Q

Translation initiation in prokaryotes

A
  1. 16S rRNA in small subunit undergoes base pairing with Shine Delgarno sequence in 5’ UTR of mRNA
  2. Initiator tRNA binds to start codon in mRNA
  3. Large ribosomal subunit binds
17
Q

Translation prokaryotes: Initiator tRNA

A

tRNA charged with N-formyl methionine

18
Q

Translation prokaryotes:
AUG codons that occur after the initial start codon use tRNA charged with N-formyl methionine?

A

False, they use different tRNA charged with methionine

19
Q

Translation initiation in eukaryotes

A
  1. 40s binds 5’ end of the cap structure
  2. 40s migrates on the 5’-UTR till the optimum AUG
  3. 60s joins 40s subunit
  4. Ribosomal complex starts translation
20
Q

Translation Eukaryotes: Initiator tRNA

A

tRNA methionine

21
Q

Translation: Elongation

A
  1. A charged tRNA binds to the A site
  2. Peptidyl transfer reaction: bond forms between the polypeptide chain and amino acid in the A site. The polypeptide is transferred to the A site.
  3. Translocation and release of tRNA: the ribosome translocates one codon to the right. The uncharged tRNA is released from the E site. Process is repeated until stop codon is reached.
22
Q

Translation: Termination

A
  1. A release factor binds to the stop codon at the A site.
  2. The polypeptide is released from the tRNA in the P site. The tRNA is then released
  3. The mRNA, ribosomal subunits, and release factors dissociate.
23
Q

Location of translation in Prokaryotes

A

Cytoplasm

24
Q

Location of translation in Eukaryotes

A

Cytosol

25
Q

Selection of a Start Codon in prokaryotes

A

Downstream from the ribosomal binding site

26
Q

Selection of a start coding in eukaryotes

A

According to Kozak’s sequences

27
Q

Termination factors in prokaryotes

A

RF1 and RF2

28
Q

Termination factors in Eukaryotes

A

ERF

29
Q

Initial binding of mRNA in prokaryotes

A

Requires a ribosomal-binding site

30
Q

Initial binding of mRNA in eukaryotes

A

Requires a 7-methylguanosine cap

31
Q

Polysomes

A

Multiple ribosomes translating the same mRNA

Biology 221 (10 decks)

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