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CBFM - M1T1 > Gene Expression > Flashcards

Gene Expression Flashcards

1
Q

What are the active sites of the ribosome?

A

A - acceptor, P - peptidyl, E - Exit

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2
Q

What are the major properties of the genetic code?

A

Specific, degenerate, universal, non-overlapping

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3
Q

What are the stop codons?

A

UAG, UGA, UAA

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4
Q

What is the process of tRNA “charging?”

A

Both an amino acid and tRNA bind the aminoacyl synthetase. The enzyme uses ATP to attach the amino acid to tRNA. Energy from this bond is later used to form the peptide bond in the peptide chain during translation.

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5
Q

What enzyme “charges” tRNA with the correct amino acid?

A

aminoacyl tRNA synthetase

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6
Q

A ribosome is 80S in size with 60S and 40S subunits. Is this ribosome prokaryotic or eukaryotic?

A

Eukaryotic

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7
Q

What RNA polymerase encodes proteins and controls translation?

A

RNA Polymerase II

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8
Q

What RNA polymerase synthesizes tRNA?

A

RNA Polymerase III

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9
Q

What is the function of RNA Polymerase I?

A

Synthesize ribosome components

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10
Q

What type of RNA makes up the most mass?

A

rRNA

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11
Q

What type of RNA is most present in the cell?

A

tRNA

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12
Q

What are the major RNA needed for protein synthesis?

A

mRNA, tRNA, rRNA

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13
Q

How does the proximal promoter differ from other enhancer elements?

A

The proximal promoter is always located close to the transcription start site and is the location where bTSFs bind.

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14
Q

Where are enhancer/silencer regions located?What is their function?

A

They may be located upstream or downstream, close by or far away on the DNA. Enhancers/silencers serve as regulatory sites where TSFs bind to change the rate of transcription

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15
Q

What is the last bTSF to bind to DNA?

A

TFIIH - Has helicase activity to unwind the DNA double helix. Also has kinase activity for phosphorylation of RNA polymerase II to initiate transcription

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16
Q

What transcription factors first binds DNA?

A

Basal transcription factors (bTSFs). These factors bind at the TATA box and result cause a low level of TFs.

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17
Q

What is the name of the site upstream from the transcription start site in eukaryotes where bTSFs bind?

A

TATA Box

18
Q

What is a DNA sequence present in both prokaryotic and eukaryotic DNA that is recognized by RNA polymerase that begins transcription?

A

Promoter

19
Q

What are the two methods of transcription termination in prokaryotes?`

A

A terminator sequence forms a stem-loop structure that causes the RNA polymerase to fall off. In DNA without a terminator sequence, a rho protein binds the mRNA to terminate transcription.

20
Q

What strand of DNA is used as the template for RNA transcription?

A

Template strand is used to transcribe RNA. mRNA is thus complementary to the template strand and exact to the coding strand, with the exception of uracil, which replaced thymine.

21
Q

What is a consensus site?

A

A protein binding site on DNA. Some nucleotides are required for protein binding, while others may vary. Proteins bind with greater affinity when their nucleotide sequence better matches that of the consensus site.

22
Q

What effect do polycistronic genes have on the size of prokaryotic genes?

A

Polycistronic genes encode various proteins. Thus, prokaryotic genes are smaller.

23
Q

What is a gene?

A

DNA segment containing information for the synthesis of polypeptides and RNA

24
Q

What is the function of the operator in prokaryotic cells?

A

A sequence of DNA in prokaryotic cells that is bound by a repressor and prevents transcription. Binding of an inducer to the operator releases the repressor for transcription to begin.

25
Q

What is the function of the lac operon in E. coli?

A

The lac operon includes genes for the uptake and metabolism of lactose. Expression is activated in the presence of lactose and highest when only lactose (and no glucose) is present.

26
Q

True/False. bTSFs are the same for every gene.

A

True. bTSFs are the same for every gene, while binding of other TSFs will vary by gene.

27
Q

What is the first of the bTSFs to bind the TATA box?

A

TFIID is the first bTSF to bind. It has a protein called TATA binding protein that binds directly to the TATA site on the DNA.

28
Q

How does a prokaryotic promoter differ from eukaryotic enhancer/silencer elements?

A

Promoters are always located upstream of the transcription start site and allows transcription to begin. Enhancer/silencer elements may be located anywhere on the DNA sequence and regulate the rate of transcription.

29
Q

What modifications must be made to mRNA after transcription in order for translation to occur?

A

Addition of a 5’ cap, splicing of introns, additional of a poly-A tail

30
Q

Where does transcription and translation take place?

A

Transcription - nucleus
Translation - cytosol

31
Q

What molecules recognize consensus sequences for intron splicing?

A

snRNPs (small nuclear ribonucleoprotein)

32
Q

Describe the process of intron splicing.

A

snRNPs recognize and bind to consensus sequences on the mRNA. Interactions between snRNPs forms a spliceosome. The intron is removed, the exon cleaved to the next exon, and the removed intron degraded.

33
Q

What accounts for the accuracy of translation? (Ensuring that the amino acid added is in fact the amino acid that was coded for)

A

Aminoacyl synthetase

34
Q

What is the start codon?

A

AUG

35
Q

Codons with mutations in the third position can often still be recognized by the same tRNA, and therefore still encode the same amino acid. This is because of degeneracy in DNA. What principle is the basis for this degeneracy?

A

Wobble

36
Q

Describe initiation of translation.

A

eIF2-GTP locates an initiator tRNA(met) and brings it to the P active site. With assistance from eIF4s, eIF2-GTP attaches tRNA(met) to the ribosome to begin reading mRNA for a start site. When a start site is reached GTP is hydrolyzed, eIF2 is released, and translation begins.

37
Q

What is a polysome/polyribosome?

A

mRNA held in circular form by eIF4 that allows for multiple ribosomes to bind and synthesize proteins following one another.

38
Q

How can eukaryotic translation be globally regulated?

A

By regulating availability of eIFs

39
Q

What enzyme forms the peptide bond between amino acids?

A

Peptidyl transferase - releases H2O

40
Q

How do diphtheria toxin and exotoxin A affect protein synthesis?

A

Act on eEFs to inhibit protein elongation

CBFM - M1T1 (42 decks)

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