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Gene expression Flashcards

1
Q

Selective gene expression allows cells to

A

efficient, synthesizing only what is needed for each cell type

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2
Q

Multicellular eukaryotes consists of and is distinguished based on

A

a mixture of specialized or differentiated cell types

based on difference in appearance and protein products

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3
Q

Cell differentiation

A

Differentiated cells are produced from groups of immature, non-specialized cells or undifferentiated cells

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4
Q

What are the five levels of gene expression

A
  1. Genome
  2. Transcription
  3. RNA processing and export
  4. Translation, and
  5. Posttranslational events
    Posttranscriptional control
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5
Q

What does Gene amplification

do?

A 
selective replication of specific genes
rRNA genes Xenopus laevis (5.8S, 18S, 28S rRNAs)
500 genes in haploid genome
4000-fold replication during oogenesis
2 million copies in mature oocyte
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6
Q

mammalian RBCs discard nuclei after enough hemoglobin mRNA is made

A

Gene deletion

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7
Q

DNA rearrangement is when

A

Movement of DNA segments from one location to another within the genome

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8
Q

DNA Methylation is associated with

A

Inactive Regions of the Genome

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9
Q

Addition of methyl groups to selected cytosine bases does what

A

silencing of gene expression

-(methylated cytosine tend to cluster near the 5’ ends of the genes – cause methylation of promoters)

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10
Q

Methylation patterns are ___ and can cause

A

inherited

causes epigenetic changes

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11
Q

some degree of chromatin decondensation (unfolding) is necessary for

A

the expression of eukaryotic genes

- to give transcription factors and RNA polymerase access to DNA

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12
Q

DNA is packaged by ____ that bid to the DNA

A

Histone proteins

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13
Q

Tagging of histone molecules by acetyl, methyl and phosphate groups has a ___ which creates ___

A

protruding tail that can be tagged which can create a histone code

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14
Q

a group of non-histone proteins associated with isolated chromatin

A

HMG

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15
Q

What has large contents of HMG

A

Transcriptionally active chromatin

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16
Q

General transcription factors – essential for transcription of all the genes transcribed by a

A

given type of RNA polymerase

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17
Q

General transcription factors assemble with RNA polymerase II at

A

the core promoter, a region immediate to start point and starts transcription at a low level

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18
Q

Regulatory transcription factors

A

increase (or decrease) transcription initiation

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19
Q

Proximal Control Elements are located

A

Located upstream (100-200 bp) & close to core promoter

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20
Q

What is the difference between activators and repressors

A

Enhancers stimulate gene expression

Silencers inhibit gene expression

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21
Q

What are the two principles govern the interaction between enhancers and the genes they regulate

A
  1. Looping - brings enhancer closer to core promoter
    1. Coactivator proteins - mediate the interaction between activators and RNA polymerase complex bound to core promoter
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22
Q

Modify chromatin/nucleosome structure

A

Coactivator proteins

– SWI/SNF family of coactivators

23
Q

What allow non-adjacent genes to be regulated in a coordinated fashion

  • turn transcription on or off
  • environmental or developmental signals
A

DNA response elements

24
Q

What is post transcriptional regulation

A

After transcription, the flow of genetic information involves a complex series of posttranscriptional events, any or all of which can turn out to be regulatory points

25
post transcriptional regulation can control by:
- RNA processing and nuclear export, - initiation factors and translational repressors, - regulation of mRNA degradation, - RNA interference and - modifications of protein structure, function and degradation
26
What does RNA processing do?
Addition of 5’ cap and a 3’ tail - Chemical modifications such as methylation - Alternative splicing – splicing together of exons removing introns, important control as it makes a variety of mRNAs from the same pre-mRNA;
27
After processing, export of mRNA through nuclear pores to the cytoplasm RNAs with defects in capping or splicing are not readily exported from the nucleus
Nuclear export
28
Transport of mRNA through nuclear pores does not take place until their export is
trigger by a stimulus signal
29
The amino acid sequence of the Rev protein includes a _____ to guide the viral RNA out through the nuclear pores into the cytoplasm
nuclear export signal
30
Once mRNA is in the cytoplasm, these are available to regulate the translation of mRNA to polypeptide
translational control mechanisms
31
Translational control mechanisms work by
- altering ribosomes or protein synthesis factors or | - regulating the activity or stability of mRNA
32
Synthesis of globin polypeptide depends on the availability of ‘heme’ which
the iron-containing prosthetic group that attaches to globin to form the final product, hemoglobin.
33
Synthesis of ferritin, an iron-storage protein, is selectively
stimulated in the presence of iron.
34
The half-life of eukaryotic mRNAs varies widely ranging from 30 minutes or less for some growth factors, and over 10 hours for the mRNA encoding β-globulin
Regulation of mRNA degradation
35
The length of poly(A) is one factor that plays a role in
controlling mRNA stability
36
are mRNA with short poly(A) tails more or less stable
less stable
37
RNA interference or RNAi – based on ability of small RNA to
trigger mRNA degradation, or inhibit mRNA translation, or inhibit transcription of the gene coding for a particular mRNA
38
RNA interference utilizes small RNAs to
to silence the expression of genes
39
RNA interference by dsRNA: A cytoplasmic nuclease known as ___ cuts dsRNA into 21-22bp fragments (siRNA)
Dicer
40
RNA interference by dsRNA: siRNA binds RISC proteins and one strand is
degraded
41
siRISC (remaining strand + RISC) binds to mRNA via
complementary base pairing
42
MicroRNAs (miRNAs) are a class of
single-stranded RNAs about 21-22 nt in length that are produced by genes found in almost all eukaryotic cells
43
miRNAs bind to and regulate
regulate the expression of mRNAs | Genes coding for miRNAs accounts for up to 5% of eukaryotic genes
44
What plays an important role in embryonic development
Translational silencing by microRNAs
45
What are Posttranslational modifications of protein structure, function
Once polypeptide chain is formed - still many ways of regulating the activity of polypeptide chain These are posttranslational control mechanisms that are available for modifying protein structure and function
46
Protein degradation are mechanisms that control the amount of any given protein present in a cell is influenced by its
rate of degradation and rate of production
47
The half-lives of cellular proteins range from a
few minutes to several weeks
48
dependent protein degradation
Ubiquitin
49
What is Ubiquitin
a small protein chain of 76 amino acids, and is joined to target proteins by a process that involves three components
50
What are the three components of Ubiquitin
E1: Ubiquitin-activating enzyme E2: Ubiquitin-conjugating enzyme E3: substrate recognition protein
51
Ubiquitin is first activated by attaching it to __ in an ATP-dependent reaction
E1
52
Activated ubiquitin is transferred to E2 and subsequently linked to __ residue in the target protein, in a reaction facilitated by E3
Lys
53
ubiquitin chains serve as targeting signals that are recognized by protein degrading structures, called
‘Proteasomes’

Cells and Molecular biology (6 decks)

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