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Biochemistry Block 4 > Regulation Of Gene Expression > Flashcards

Regulation Of Gene Expression Flashcards

1
Q

Gene expression results in the production of

A

Either RNA or protein

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2
Q

Describe each of the following kind of genes:

  1. Housekeeping genes
  2. Regulated genes
A
  1. Involved in basic cellular function, constitutively expressed and not regulated
  2. Required only in certain cell types/ certain conditions; subject to various control mechanisms that will determine if these genes will be expressed
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3
Q

Regulation of gene expression in pro:

  1. 2 regulatory molecules and their function
  2. 2 types of operons and their function
A
  1. Repressors and activators: suppress/increase transcription of a gene
  2. Inducible - transcription is usually OFF but can be stimulated
    Repressible- transcription is usually ON but can be inhibited
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4
Q

Lac operon:

  1. Prokaryotes or eukaryotes?
  2. Inducible or repressible?
  3. When would it be induced
  4. What type of bacteria uses this
A
  1. Prokaryotes
  2. Inducible (only inducible one we need to know)
  3. When glucose is absent but another sugar is present
  4. E. coli
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5
Q

Lac operon

  1. When only glucose is present, lac operon is on or off?
  2. Repressor protein is encoded by? Where is it? What enzyme does it block?
  3. Glucose inhibits what enzyme? What would this cause?
A
  1. Off
  2. LacI gene; always present and bound to the operator; blocks RNA polymerase
  3. Adenylyl cyclase -> no cAMP, cannot form CAP/cAMP complex, cannot initiate transcription
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6
Q

Lac operon continued:

  1. If only lactose is present, is it on or off?
  2. When glucose is absent what happens
  3. When lactose is present, what is produced? What is it and what does it do
A
  1. On
  2. Adenylyl cyclase makes cAMP, CAP/cAMP complex forms, binds to CAP binding site, RNA polymerase can initiate transcription
  3. Allolactose (small amount), isomer of lactose produced from lactose, binds to the repressor and prevents it from binding to the operator (so gene is not blocked)
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7
Q

Lac operon continued:

  1. When both lactose and glucose are present, lac operon is on or off?
  2. Is repressor active or inactive?
  3. Then why can’t transcription be initiated?
A
  1. Off
  2. Inactive
  3. CAP site is empty because glucose is present
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8
Q

Eukaryotes are different because they have gene expression regulation at 5 different levels. Give an example

  1. Transcriptional
  2. Posttranscriptional
  3. Translational
  4. Posttranslational
  5. Epigenetic
A
  1. PEPCK
  2. Alternative splicing/mRNA editing
  3. EIF-2
  4. Modifications of polypeptide chain
  5. Modifications of DNA
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9
Q

Transcriptional control:

  1. Regulatory sequences of DNA are usually embedded __
  2. Define cis-acting elements
  3. Why are regulatory sequences of DNA called cis-acting
  4. Interact with? Which are?
  5. Trans-acting regulators are __
A
  1. Noncoding region of the genome
  2. DNA sequences bound by trans-acting regulatory molecules (enhancers)
  3. They influence expression of genes only on the same chromosome
  4. Regulatory molecules (transcription factors) which are trans-acting regulators
  5. Proteins
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10
Q

Binding of trans-acting regulators to DNA is achieved by one of which 3 things?

A

Zinc finger, leucine zipper, helix-turn-helix in protein

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11
Q
  1. Define enhancer
  2. Can be located?
  3. When can they act in a tissue specific manner?
A
  1. DNA sequences that increase rate of initiation of transcription
  2. Close or far from the gene, or even within intron regions of other chromosomes (typically on same chromosome tho)
  3. If the DNA binding proteins (transcription factors) are only present in certain tissues
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12
Q
  1. How can enhancers be brought close to the basal promoter
  2. Transcription factors are cis or trans?
  3. Transcription factors interact with RNA polymerase II to stabilize formation of __ and recruit?
A
  1. By bending the DNA molecule
  2. Trans
  3. Initiation complex and recruit chromatin modifying proteins (histone acetylase)
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13
Q

PEPCK gene expression is induced by __ which diffuses into ?

A

Cortisol; hepatocyte

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14
Q
  1. Function of alternative splicing

2. Give an example

A
  1. To make tissue specific isoforms of proteins from the same pre-mRNA
  2. Tropomyosin
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15
Q
  1. MRNA editing is what type of control?

2. Example: how does apo B100 get changed to apo B48

A
  1. Post-transcriptional

2. CAA codon for glutamine is deaminated to U (UAA) which is a stop codon - makes protein shorter (only gets 48% of)

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16
Q

MRNA stability:

  1. RNAi (interference) reduces gene expression by either of what 2 things
  2. Plays a role in what 3 processes
  3. Has huge __ potential
A
  1. Repressing translation and increasing degradation of specific mRNAs
  2. Cell proliferation, differentiation, and apoptosis
  3. Therapeutic
17
Q
  1. RNAi is mediated by? How many base pairs does it have?
  2. MiRNA acts as ?
  3. Works with RISC-RNA-induced silencing complex to do what?
  4. What can also trigger RNAi?
A
    1. MicroRNA (miRNA) ~20-22 bp
      1. Guide strand (contains complementary sequence)
      2. Block translation
      3. SiRNA
18
Q

Translational control:

  1. Phosphorylation of eIF-2 inhibits its function how?
  2. Name some things that would activate kinases to phosphorylate eIF-2 (4)
A
  1. By inhibiting GDP-GTP exhange thus inhibiting translation at the initiation step
  2. Amino acid starvation, heme deficiency, presence of double stranded DNA, accumulation of misfolded proteins in the rER
19
Q
  1. Why is cleavage/trimming necessary for many proteins? Example
  2. Protein degradation is done by
A
  1. To become functionally active; protein digestion enzymes

2. Ubiquitination

20
Q

Euchromatin vs heterochromatin

A

Euchromatin= loose, accessible for transcription

Heterochromatin= tightly packed, inaccessible

21
Q

Epigenetic regulation:

  1. What are CpG islands
  2. Methylation of DNA/histones causes? Genes are expressed or no?
  3. Histone acetylation causes? Genes are expressed or no?
A
  1. Regions in DNA rich in CG that are prone to modifications
  2. Nucleosomes tightly pack together; genes are not expressed
  3. Nucleosomes are loosely packed; genes are expressed
22
Q
  1. What are transposons
  2. Direct vs replicative movement
  3. Transposition contributes to __
  4. Transposition is associated with what 3 diseases/conditions?
A
  1. Mobile segments of DNA that move in a random manner from one site to another one same or different chromosome
  2. Direct=cuts out and inserts transposon at a new site; replicative= transposon is copied and inserted elsewhere while original remains in place
  3. Structural variation in the genome
  4. Hemophilia A (rare), duchenne muscular dystrophy, antibiotic resistance in bacteria

Biochemistry Block 4 (9 decks)

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