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Chromosomes and genes > Lecture 13 and 14 > Flashcards

Lecture 13 and 14 Flashcards

1
Q

What is transfer RNA?

A

An adapter RNA molecules that interfaces with single amino acids

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2
Q

What is mRNA?

A

An RNA transcript of DNA code

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3
Q

What is ribosomal RNA?

A

Aligns the message in a ribosome so the codons can be coded

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4
Q

What does rRNA play a role in catalysing?

A

Joining of amino-acids togehter

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5
Q

mRNA is not as _____ as the original DNA is has copied

A

robust

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6
Q

mRNA creates great ________ with respect to how the information is used

A

flexibility

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7
Q

RNA polymerase binds with the help of the ______

A

sigma factor

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8
Q

RNA creates what type of complex as it moves along the DNA?

A

Open complex

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9
Q

RNA is synthesised in which direction?

A

5’ to 3’

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10
Q

What recursors are used in RNA synthesis?

A

Ribonucleotide triphosphate

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11
Q

What is released as the RNA is synthesised?

A

Pyrophosphate

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12
Q

Bacterial genes have ______ regions.

A

Promoter

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13
Q

What is rho-independent termination?

A

Mechanism for stopping transcription in prokaryotes

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14
Q

How does rho-independent termination create a hairpin?

A

mRNA molecules has sequence with high proportion of C and G, which bond to one another forming RNA duplex and hairpin structure

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15
Q

What happens when the mRNA molecule forms a hairpin?

A

Succeeded the hairpin is a chain of uracil, which has weak bonds with adenine, a protein on RNA polymerase binds to the hairpin structure, causing temporary lapse.

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16
Q

What happens when there is a temporary lapse in mRNA transcription?

A

The hairpin structure unwinds and dissociates from RNA polymerase, terminating transcription

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17
Q

What is the rho protein?

A

An ATP dependent helicase made of 6 identical subunits

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18
Q

How is rho initiated?

A

Sites rich in cytosine, poor in guanine

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19
Q

What direction does rho move along the molecule in?

A

5’ to 3’

20
Q

How does rho disrupt the transcriptional complex?

A

Acts as RNA/DNA helicase when it reaches transcriptional bubble

21
Q

What forms when rho protein reaches the termination signal?

A

A polypeptide loop of rho protein, stops elongation byu being inserted into RNA polymerase complex

22
Q

What enzyme catalyses attachment of tRNAs to corresponding amino acids?

A

Aminoacyl-tRNA syntetase

23
Q

The prokaryotic ribosomes consists of which subunits and what overall ribosome?

A

30S, 50S, 70S

24
Q

The eukaryotic ribosome consist of which subunits and what overall ribosome?

A

60S, 40S, 80S

25
Q

What sites make up the large subunit of the ribosome?

A

Peptidyl (P) site
Aminoacyl site (A)
Peptidly transferase

26
Q

What name is given to the start of polypeptide synthesis?

A

Initiation

27
Q

What is the start codon and at what end of the mRNA is it?

A

AUG

5’ end

28
Q

What is the amino acid on the initiation tRNA for prokaryotes? Eukaryotes?

A

Formalmethionine (fMet)

methionine

29
Q

What is the second stage of translation?

A

Elongation

30
Q

Ribosomes move in which direction during translation?

A

5’ to 3’

31
Q

To which terminus are amino acids added?

A

C

32
Q

How many amino acids are added during translation per second?

A

2-15

33
Q

What name is given to the process that halts translation?

A

Termination

34
Q

What triggers termination?

A

Nonsense codon at 3’ end of reading frame

35
Q

What happens when a nonsense codon is recongised?

A

Release factor proteins halt polypeptide synthesis

36
Q

In prokaryotes, where does the small ribosomal subunit bind?

A

Ribosome binding site, (shine dalgarno box and initiating codon)

37
Q

What is the shine dalgarno sequence?

A

Ribosomal binding site located around 8 bases upstream of start codon AUG, aligns ribosome with start codon

38
Q

What is the wobble rule?

A

Some tRNA’s recognise more than one codon for amino acids they carry

39
Q

What process deletes introns?

A

Posttranscriptional splicing

40
Q

What three things happen when RNA is processed after transcription in eukaryotes?

A

5’ methylated cap added
3’ Poly A tail added
Spliced to generate mature message

41
Q

What does the poly-A tail do?

A

Direct the RNA out of the nucleus

42
Q

How is a poly-A tail added to the 3’ end?

A

Cleavage by ribonuclease

Poly-A polymerase adds A’s to 3’ end

43
Q

Give an example of a gene with many introns.

A

Dystrophin gene

Underlies Duchenne muscular dystrophy

44
Q

What sequences dictate where splicing occurs?

A

Splice donor, branch site, splice accpetor

45
Q

How are introns removed?

A

two sequential cuts, (loop first produced called lariat)

46
Q

What type of enzyme catalyses splicing?

A

Spliceosomes

47
Q

What enzyme ensure splicing reactions take place in concert?

A

Ribozymes (RNA molecules that act as enzymes)

Chromosomes and genes (10 decks)

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