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Exam 4 Biology Sets > Chapter 17: Gene Expression > Flashcards

Chapter 17: Gene Expression Flashcards

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1
Q

What carries out transcription?

A

RNA polymerase

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2
Q

Explain how RNA polymerase works in transcription.

A
  • builds RNA 5’ —> 3’
  • does not require a primer
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3
Q

Where does transcription begin?

A

at the 3’ of a promoter

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4
Q

What is a promoter?

A

short sequence of DNA where proteins bind to initiate transcription

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5
Q

Describe promoters in bacteria.

A

contain -35 box and -10 box

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6
Q

Describe promoters in eukaryotes.

A

promoters are variable

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7
Q

What are transcription factors?

A

proteins that bind to DNA and are involved in the process of transcription

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8
Q

What are the transition factors in bacteria?

A

sigma factors

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9
Q

Describe sigma factors.

A
  • primary is sigma 70
  • detachable subunit of RNA polymerase
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10
Q

Describe the binding of sigma factors.

A
  • sigma looks for a specific site on the promoter
  • binds first to DNA (-10/-35 boxes), then guides the RNAP to where transcription will begin
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11
Q

What happens to sigma when transcription begins?

A

detaches from the core enzyme, then the core enzyme continues transcribing

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12
Q

Describe the RNAP holoenzyme.

A
  • only in bacteria
  • means “whole enzyme” (holo=whole)
  • is a sigma + core enzyme
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13
Q

What are the 3 overall steps of transcription?

A
  1. initiation
  2. elongation
  3. termination
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14
Q

What is the initiation step of transcription?

A
  1. RNAP binds to sigma, sigma binds to promoter
  2. RNAP opens DNA to begin transcription
  3. sigma released, which allows RNAP to continue transcribing
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15
Q

What is the elongation step of transcription?

A
  • RNAP continues transcribing
  • RNAP moves along DNA continuously
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16
Q

What is the termination step of transcription?

A
  1. a termination signal is transcribed from RNAP and folds into hairpin
  2. hairpin causes the release of RNA from RNAP
  • THINK HAIRPIN=TERMINATOR
  • at dance, hairpin hurt head SO BAD, so you terminate it and causes a release of hair
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17
Q

What are some differences between eukaryotic transcription and bacterial transcription?

A
  1. euks have 3 RNA polymerases (one for each type of rna), proks have 1
  2. euks have diverse promoters
  3. euks=general transcription factors (and mu;tiple required for initiation of transcription); proks=sigma
  4. euks have multiple methods of termination (poly(A) signal)
  5. euks= separate transcription and translation
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18
Q

What is the poly (A) signal?

A

termination downstream of a long stretch of A nucleotides

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19
Q

Describe RNA processing in eukaryotes.

A

DNA –> pre-mRNA –> mature mRNA

DNA to pre-mRNA = transcription
pre-mRNA to mature mRNA = RNA processing

20
Q

What are exons?

A

genes that remain part of mRNA (EXons=EXpressed)

21
Q

What are introns?

A

sections removed from mRNA (INtrons=INtervene)

22
Q

Describe the 3 steps of RNA processing (splicing).

A
  1. snRNPs assemble, then bind the the pre-mRNA
  2. snRNPs assemble to form the spliceosome
  3. the intron is cut out/removed as a ‘lariat’ structure (snRNAs/ribozymes perform the cleavage)
23
Q

What are the cap and tail in RNA processing?

A

cap: 5’ cap (modified GTP added to 5’ end)
tail: poly (A) tail (long chain of As added to 3’ end)

24
Q

What are the functions of having a cap and tail in RNA processing?

A
  1. enables ribosome to bind to the mRNA
  2. protects mRNA from degradation by ribonucleases (RNases)
25
Q

What does the tRNA secondary structure do?

A

separates amino acids from codons

26
Q

List and describe the structures of the secondary tRNA structure.

A
  1. amino acid: SER amino acid is attachment site for amino acids at 3’ end
  2. stems: created by hydrogen bonding between complementary base pairs
  3. loops: consist of unpaired bases
  4. anticodon: allows tRNA to recognize a codon
  5. codon: codes for specific amino
27
Q

List and describe the structures of the tertiary tRNA structure.

A
  1. amino acid attached to CCA/SER amino acid (reading 5’–>3’) at 3’ end
  2. contains single stranded loops, but double stranded stems
  3. contains codon and anticodon
28
Q

What is aminoacyl tRNA?

A
  • tRNA + amino acid
  • “charged” tRNA
29
Q

How do codons and anticodons relate?

A

they are complementary and antiparallel

30
Q

What are aminoacyl-tRNA synthetases?

A
  • catalyze the addition of amino acids to tRNAA
31
Q

What are the 2 domains in tRNAs and their functions?

A
  1. catalytic: binds specific amino acids
  2. anticodon binding: binds specific tRNA
32
Q

How many different aminoacyl-tRNA synthetases are there?

A

20 with specific active sites

33
Q

How many different tRNAs are there?

A

40-45

34
Q

What is the wobble hypothesis?

A

bases at the 3’ end of a codon can bind anticodons in ways that don’t match watson-crick base pairing

  • allows tRNA to read more than one codon
35
Q

What is ribonucleoprotein?

A

made of protein and rRNA

36
Q

What is a ribozyme?

A

rRNA catalyzes peptide bond formation

37
Q

List and describe the 3 binding sites of a ribosome.

A
  1. A site: Aminoacyl tRNA
  2. P site: tRNA with growing polypeptide attached
  3. E site: tRNA that will exit
38
Q

Describe the two main structures of a ribosome.

A
  1. small subunit: holds mRNA
  2. large subunit: contains tRNA binding sites; where peptide bond formation occurs
39
Q

What are the 3 overall steps of translation?

A
  1. initiation
  2. elongation
  3. termination
40
Q

Describe the steps of initiation in translation.

A
  1. mRNA binds to small subunit of ribosome
  2. first aminoacyl tRNA binds to start codon
  3. large subunit of ribosome binds; 1st tRNA in P site
41
Q

Describe the steps of elongation in translation.

A
  1. new aminoacyl tRNA enters A site
  2. peptide bond forms between amino acids
  3. ribosome moves one codon (translocates)
  4. process repeats: polypeptide chain extends while ribosome moves along the mRNA
42
Q

Describe the steps of termination in translation

A
  1. release factor binds to stop codon
  2. polypeptide and tRNAs released
  3. ribosome subunits separate
43
Q

What are the 2 post-translational modifications?

A
  1. protein folding
  2. chemical modifications
44
Q

What is protein folding?

A
  • folding determined by the amino acid sequence
  • spontaneous most of the time
  • guided and accelerated by molecular chaperones
45
Q

What are chemical modifications?

A
  • within rough ER and golgi
  • phosphorylation, glycosylation (protein tagging), activation
46
Q

What are the 4 main steps of eukaryotic gene expression?

A
  1. transcription
  2. rna processing
  3. translation
  4. post-translational modification

Exam 4 Biology Sets (7 decks)

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