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MCBG > Gene Expression > Flashcards

Gene Expression Flashcards

1
Q

In which direction is mRNA produced?

A

In the 5’—->3’ direction

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2
Q

In which direction are proteins made?

A

From the n terminus end to the c terminus end

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3
Q

A gene is not a direct code for a protein, part of it is…

A

Introns (spliced out)

Initiation and termination signals

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4
Q

Making a polypeptide/polynucleotide/dna replication follows which 3 stage process?

A

Initiation
Elongation
Termination

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5
Q

How is dna replication initiated?

A

Recognition of origin of replication

Initiation proteins recruit DNA polymerase

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6
Q

In both DNA replication and transcription, what happens in the elongation stages?

A

There is 5’—>3’ chain growth

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7
Q

When is DNA replication terminated?

A

When replication forks meet

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8
Q

How is transcription initiated?

A

Recognition of the promoter region

Transcription initiation factors recruit rna polymerase

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9
Q

How is transcription terminated?

A

Dependent on the sequence

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10
Q

What are the promoter regions?

A

Signals that tell the transcription where to start

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11
Q

What is the transcription unit?

A

The promoter region + the gene coding for the protein

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12
Q

What does every promoter region contain?

A

A TATAAA box sequence in the 5’—>3’ direction

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13
Q

How is transcription initiated?

A

Binding of transcription initiation factors to TATAAAA box of the promoter region —> recruitment of rna polymerase

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14
Q

When does transcription begin?

A

The +1 point after RNA polymerase binds

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15
Q

What does rna polymerase do during the elongation phase of transcription?

A

Unwinds 2 dna strands, reads template strand in 3’–>5 direction —> produces mRNA in the 5’—>3’ direction

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16
Q

What are the two dna strands called in transcription?

A

Coding strand

Template strand

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17
Q

What is the purpose of RNA processing? When does it happen?

A

To protect the mRNA

Happens immediately while mRNA is being made

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18
Q

What are 3 different ways in which mRNA is processed?

A

Capping
Tailing (polyadenylation)
Splicing

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19
Q

What is capping?

A

Cap created at the 5’ end to prevent against degradation - 5’-5’ linkage is created

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20
Q

What is tailing/polyadenylation?

A

At the 3’ end, a polyA (200+ bases long) tail added to protect against degradation

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21
Q

Which enzyme adds the polyA tail to mRNA?

A

PolyA polymerase

22
Q

What is splicing of an mRNA molecule?

A

Introns that do not code for the protein are spliced out by endocnucleases

23
Q

Ribosomes which exist freely in the cytoplasm usually form which shape? What is the structure called?

A

A spiral shape

Polysome

24
Q

What is the length of a prokaryotic ribosome? What type of ribosome exist in prokaryotes?

A

20nm

70S

25
Q

What is the length of a eukaryotic ribosome? What type of ribosomes exist in eukaryotes?

A

32nm

80S

26
Q

What does a 70S prokaryotic ribosome consist of?

A

2 sub units; 50S and 30S

3rRNAs + 56 proteins

27
Q

What does an 80S ribosome consist of?

A

2 sub units; 60S and 40S

4rRNAs + 82 proteins

28
Q

What are the majority of the proteins found in 70s and 80s ribosomes?

A

Enzymes for translation

29
Q

What are the three main types of RNA? By which enzyme are each of them produced?

A 
Ribosomal RNA (rRNA) - RNA polymerase I
Messenger RNA (mRNA) - RNA polymerase II
Transfer RNA (tRNA) - RNA polymerase III
30
Q

The majority of RNA found in our cells is…

A

Ribosomal RNA

31
Q

There are around _____ different kinds of tRNA

A

~100 different kinds

32
Q

The genetic code is degenerate, what does this mean?

A

There are 20 amino acids and 64 different codons, this means that 1 amino acid can be coded for by more than 1 codon.

33
Q

What is the structure of a tRNA molecule?

A

Single stranded

Clover model

34
Q

What property of RNA allows tRNA to form this clover shape?

A

RNA is able to make stem loops, where hydrogen bonds are formed between anti-parallel complementary sequences

35
Q

Where does the amino acid bind to on a tRNA molecule?

A

At the 3’ (-OH) end

36
Q

Proteins always begin with which amino acid?

A

AUG - methionine

37
Q

Translation is terminated by stop codons, what are the stop codons?

A

UAG, UGA, UAA

38
Q

Each tRNA contains a __________ anticodon to the amino acid it recruits

A

Complementary

39
Q

What bases exist at tRNA anticodons to allow the degeneracy/flexibility of the genetic code? What are bases at this position called?

A

I bases

Wobble bases

40
Q

Which bases occupy the wobble base position on the codon and anticodon?

A

The 5’ base of the anticodon

And the 3’ base of the codon

41
Q

What happens at initiation during translation?

A

Methionine connected to tRNA binds to 5’ cap of mRNA with the 40S sub unit of the ribosome
Sub unit moves along until AUG codon found (energy required)
Fully functional ribosome formed (energy required)

42
Q

A ribosome can recognise how many codons at one time? What two sites does a ribosome have?

A

2

A site and a P site

43
Q

Which enzyme helps with the formation of peptide bonds at ribosomes?

A

Peptidyl transferase

44
Q

What happens during the elongation stage of translation?

A

Binding of the complementary amino-acyl tRNA
Peptide bond formed at the A site
Uncharged tRNA at P site released from ribosome
Translocation (using ATP), growing chain at P site, A site empty

Process continues….

45
Q

When does termination occur in translation?

A

When a stop codon appears at A site

46
Q

What happens during termination in translation?

A

Stop codon appears at A site
Bond between peptide and tRNA broken with H2O
Leaves uncharged tRNA molecule and peptide
Peptide released leaving empty ribosome

47
Q

What is the complex of proteins that splices out the introns in a pre-RNA molecule called?

A

Spliceosome

48
Q

In any mRNA molecule there are two UTR (untranslatable regions) - where are these found? What is the sequence between these two points called?

A

Before the initiation codon
After the stop codon

Open reading frame

49
Q

What are some features of translation in bacteria?

A

It is coupled with transcription
Only one type of rna polymerase
No post transcriptional modification

50
Q

Give an example of a drug affecting bacterial translation by affecting prokaryotic ribosomes?

A

Erythromycin - binds to the 50S ribosomal subunit

Prevents translocation

MCBG (15 decks)

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