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Cell Bio > L5. Gene expression & protein synthesis I > Flashcards

L5. Gene expression & protein synthesis I Flashcards

1
Q

explain the cellular control of gene expression

A
  • if cell A in an organism needs protein A, it will make a lot of transcripts for protein A, upregulating it, but not a lot of protein B, deregulating it
  • if cell B in the same organism needs protein B, it will up regulate protein B while deregulating protein A
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2
Q

cellular control of gene expression - stem cells

A
  • cells that can differentiate into different kinds of cell
  • can do this through up regulation and deregulation of certain proteins
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3
Q

define transcription

A

an ongoing process which occurs in many places at the same time (even for the same gene)

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4
Q

how is RNA different from DNA

A
  • single strand
  • U instead of T
  • ribose sugar
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5
Q

how is DNA different from RNA

A
  • double strand
  • T instead of U
  • deoxyribose sugar
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6
Q

DNA - what is the coding strand

A
  • oriented in a 5’ to 3’ fashion
  • looks like the finished mRNA
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7
Q

DNA - what is the template strand

A
  • oriented in a 3’ to 5’ fashion
  • strand that is used to make the mRNA
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8
Q

explain the intramolecular base-pairing of RNA

A
  • RNA is not linear, it may go conventional or nonconventional base pairings
  • it can form 3D structures to allow things to bind to it and interact with it
  • these structures all have different functions
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9
Q

intermolecular base-pairing of RNA - conventional vs nonconventional base pairing

A
  • conventional base pairing: A-U, G-C
  • nonconventional: G-U, C-A
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10
Q

explain how RNA polymerase carries out transcription

A
  • since DNA is not hydrogen bounded, it can be easily displaced and allow the RNA pol to transcript the code
  • RNA pol uses mRNA molecules from 5’ to 3’
  • to begin translation, it jumps onto the promoter region and recognizes the start codon
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11
Q

how is RNA pol different from DNA pol

A
  • uses ribonucleotides
  • doesn’t need a primer for transcription
  • does not have the capacity for proofreading
  • more mistakes
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12
Q

how is DNA pol different than RNA pol

A
  • uses dNTPs
  • needs primers for transcription
  • does have the capacity for proofreading
  • less mistakes
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13
Q

RNA pol vs DNA pol - why did RNA pol evolve to be mistake prone and DNA pol did not

A
  • if there is a mutation in an mRNA, the mutation will be passed onto a small number of proteins
  • if there is a mutation in DNA, then the mistake impacts the whole cell and thus all of the protein
  • so its less dangerous if there is a mutation in RNA
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14
Q

explain the types of RNA molecules

A
  • messenger RNAs (mRNAs)
  • ribosomal RNAs (rRNAs)
  • microRNAs (miRNAs)
  • transfer RNAs (tRNAs)
  • other noncoding RNAs
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15
Q

types of RNA - mRNA function

A

code for proteins

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16
Q

types of RNA - rRNA function

A
  • form the core of the ribosome’s structure
  • catalyze protein synthesis
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17
Q

types of RNA - miRNA function

A

regulate gene expression

18
Q

types of RNA - tRNA function

A

serve as adaptors between mRNA and amino acids during protein synthesis

19
Q

types of RNA - other noncoding RNA function

A
  • used in RNA splicing
  • gene regulation
  • telomere maintenance
  • many other processes
20
Q

explain transcription in bacteria

A

bc there is no nucleus, transcription of mRNA and translation into a protein can happen at the same time

21
Q

bacterial transcription - sigma factor

A
  • recognizes promoter region and tells RNA pol to make mRNA
  • it zips along the DNA (without unwinding it) with RNA pol until is encounters a promoter region
  • then mRNA is made
22
Q

bacterial transcription - promoter

A
  • tells RNA pol to make mRNA
  • has certain repeat sequences
  • it is upstream of the starting point for RNA synthesis
  • it will not be in the mRNA when transcription is done
23
Q

how can genes be transcribed in different directions

A
  • polymerases can use either on of the DNA strands as a template
  • the promoter is always near the 3’ end and transcription occurs in the opposite direction towards 5’
24
Q

how is prokaryotic RNA pols different than eukaryotic pols

A
  • 1 RNA pol
  • not a lot of regulatory elements
  • genes are closer together
  • RNA pol and sigma factor initiates transcription
25
Q

how is eukaryotic RNA pols different than prokaryotic RNA pols

A
  • 3 RNA pols
  • RNA pols need accessory proteins: general transcription factors
  • transcription initiation is more complicated
  • many regulatory sequences, more complex regulation, genes further apart
  • transcription has to take into account DNA packaging (nucleosomes)
26
Q

eukaryotic transcription - RNA pol I

A

transcribes most rRNA genes

27
Q

eukaryotic transcription - RNA pol II

A

transcribes:
- all protein-coding genes
- miRNA genes
- plus genes for noncoding RNAs

28
Q

eukaryotic transcription - RNA pol III

A

transcribes: tRNA genes, 5S rRNA gene, and genes for many other small RNAs

29
Q

explain eukaryotic transcription

A
  • first, a transcription factor needs to find the TATA box (the promoter region)
  • another transcription factor will recruit RNA pol to the box
  • another transcription factor hydrolyzes ATP for energy
  • another transcription factor uses the energy to phosphorylate the pol tail to allow enzymes to bind on it
30
Q

eukaryotic transcription - what enzymes bind on the pol tail

A
  • enzymes for capping, splicing, and polyadenylation
  • the polyadenylation signal, signals the end of transcription
31
Q

eukaryotic transcription - explain RNA processing

A
  • RNA as to be processed before leaving the nucleus
  • to leave the nucleus, it has to have a 5’ cap and a poly-A tail
32
Q

eukaryotic transcription: mRNA processing - mRNA capping

A
  • this refers to the modification of the mRNA 5’ end
  • the capping results in an addition of a guanine with a methyl group
  • happens when ~25 nucleotides have been transcribed
33
Q

eukaryotic transcription: mRNA processing - polyadenylation

A
  • first, the 3’ end is trimmed by an enzyme
  • next, a second enzyme adds a series of repeated adenines
  • happens after the noncoding sequence
  • this attracts relevant proteins to bind onto the RNA pol II tail
34
Q

eukaryotic genes - introns

A
  • noncoding sequence
  • cut by splicing factors before final mRNA is released
35
Q

eukaryotic genes - exons

A
  • represented in the open reading frame as coding sequences
  • splicing factors glue them together after introns are taken out
36
Q

eukaryotic genes - why is it advantageous to have more introns

A
  • alternative splicing
  • Can splice these in difference combinations and get different functions
  • different versions of the same protein, made from the same gene, but with different functions
37
Q

explain the splicing process

A

the spliceosome complex facilitates removal of intron and splicing of exons

37
Q

how is mature mRNA reconigzed

A
  • by RNA-binding proteins
  • they recognize the 5’ cap, poly-A tail, and exon junctions and the mRNA will be exported out of the nucleus
37
Q

splicing process - what is it regulated by

A
  • snRNPs (small nuclear ribonucleic proteins)
  • they interact with the spliceosome complex and recognizes exon-intron boundaries and removing introns
38
Q

mature mRNA - what happens in the cytosol before translation

A

protein exchange in which 5’ cap binding protein is swapped for translation initiation factors

Cell Bio (21 decks)

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