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Cell Bio > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

All of the cell types that make up an organism
share the same

A

genome

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2
Q

enables cells to selectively
control the synthesis of the RNAs and proteins in
their genome

A

gene expression

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3
Q

First step of gene expression:

A

Transcriptional control

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4
Q

Control the rate at which DNA is
transcribed into mRNA is what step in gene expression

A

1st, transcriptional control

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5
Q

This is the most efficient (but slowest) way to control gene expression is through

A

transcriptional control

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6
Q

Transcription is initiated at the

A

promoter

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7
Q

The __ is located upstream of (a.k.a. before) the starting
point for RNA synthesis

A

promoter

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8
Q

What must bind to the promoter to begin transcription

A

RNA polymerase

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9
Q

most genes include ___
that are used to switch the gene on or off

A

regulatory DNA sequences

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10
Q

Regulatory DNA sequences are bound by proteins called

A

transcription regulators

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11
Q

Each transcription regulator recognizes __, and regulates __

A

different DNA sequences, distinct genes

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12
Q

Most transcription regulators fit into the __ of the DNA
double helix and form ___ in the groove

A

major groove, contacts with the nucleotide pairs

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13
Q

Each individual contact with the transcription regulators and nucleotide pairs is __

A

weak

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14
Q

How many contacts form between the protein and the DNA so the interaction is strong and specific

A

10-20

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15
Q

Regulatory DNA sequences are found where? located where?

A

found in nearly all genes, located near to or in promoters

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16
Q

Transcription regulators bind to

A

DNA sequences

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17
Q

Transcription regulators can act as

A

activators or repressors by switching the gene on or off

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18
Q

transcription regulators regulate binding of

A

RNA polymerase to the promoter

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19
Q

use simple switches to control gene expression in response to their environment

A

bacteria

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20
Q

Genes that encode proteins that work together are often clustered together on the chromosome and transcribed from a

A

single promoter

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21
Q

gene clusters are called

A

operons

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22
Q

Operons are common in __ but rare in __

A

bacteria, eukaryotes

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23
Q

The tryptophan operon (a.k.a. Trp operon) __that synthesize tryptophan

A

contains five genes that
encode enzymes

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24
Q

The tryptophan repressor regulates

A

expression
of the Trp operon

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25
Q

The operon’s promoter sequence contains a regulatory sequence called the

A

operator

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26
Q

If tryptophan is ___ there’s no need to synthesize more

A

already available

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27
Q

The tryptophan repressor binds the operator only if….

A

it is also bound to tryptophan

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28
Q

What occurs in the absence of tryptophan…

A

Trp repressor is inactive and does not bind the
operator, so transcription can proceed

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29
Q

When the tryptophan repressor is bound to the operator….

A

it blocks access of
RNA polymerase to the promoter, preventing transcription of the operon

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30
Q

The Lac operon is controlled by two transcription
regulators:

A

activator and repressor

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31
Q

The Lac operon is turned on in the absence of __ and
the presence of __

A

glucose, lactose

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32
Q

The Lac operon encodes proteins necessary to import and digest

A

lactose

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33
Q

The Lac operon is controlled by the

A

CAP activator and Lac repressor

34
Q

When glucose is not available, the bacterium makes

A

cAMP, which binds to CAP activator

35
Q

The CAP activator must bind

A

cAMP to bind DNA

36
Q

Lactose (or allolactose) binds the

A

Lac repressor and prevents it from binding DNA

37
Q

The Lac repressor only binds DNA in the

A

absence of lactose

38
Q

To activate gene expression, the CAP activator must __ and the lac repressor must __

A

bind DNA, not bind DNA

39
Q

Eukaryotic transcription regulators control gene
expression…

A

from a distance

40
Q

Eukaryotic gene activators bind DNA sites called

A

enhancers

41
Q

The DNA between the enhancer and the promoter forms a

A

loop to bring the activator protein close to the promoter

42
Q

The most important adaptor is a large protein complex called the

A

Mediator

43
Q

positions the general transcription factors and RNA
polymerase at the promoter

A

mediator complex

44
Q

Histone acetyltransferases attach

A

acetyl groups to histones

45
Q

Acetyl groups recruit

A

transcription activators

46
Q

uses ATP to alter the arrangement of
nucleosomes on the DNA

A

Chromatin-remodeling complex

47
Q

Transcription regulators work together to

A

regulate gene expression

48
Q

Dozens of __ bind regulatory sequences that can
be spread over thousands of nucleotides

A

transcriptional regulators

49
Q

A single transcription regulator can coordinate the expression of

A

many genes

50
Q

A master transcription regulator that controls eye development

A

ey

51
Q

controls expression of multiple genes by binding regulatory DNA sequences

A

Ey

52
Q

Some genes controlled by Ey encode

A

additional transcription regulators

53
Q

Ey is so powerful that it can

A

activate its regulatory network outside its normal
location

54
Q

Differentiated cells maintain their identity through

A

“cell memory” mechanisms

55
Q

After a cell is differentiated into a particular cell type, its
progeny cells

A

will remain the same cell type

56
Q

To maintain cell identity, the pattern of gene expression must be

A

passed onto daughter cells

57
Q

3 mechanisms of cell memory

A
  • Positive feedback loops
    • DNA methylation
    • Histone modifications
58
Q

Transmission of gene expression patterns to daughter cells without change in DNA sequence

A

Epigenetic inheritance

59
Q

In positive feedback loops, the transcription factor…

A

activates its own gene

60
Q

Each time e the cell divides, the transcription factor is distributed to both daughter cells, so it continues to stimulate the

A

positive feedback loop

61
Q

DNA methylation occurs on many __, but only those __

A

cytosines, adjacent to guanine

62
Q

Inhibits gene expression by recruiting transcriptional repressors

A

DNA methylation

63
Q

Important for maintaining distinct cell types

A

DNA methylation

64
Q

Following DNA replication, methylated cytosines act as molecular tags that recruit

A

maintenance methyltransferase

65
Q

maintenance methyltransferase ensures that the

A

same methylation pattern is copied to the new
DNA strand

66
Q

With histone modifications, each daughter cell inherits

A

half of its parent’s histone proteins

67
Q

bind modified histone tails and confer the same modifications
to neighboring histones

A

enzymes

68
Q

Cells can exert post-transcriptional control by controlling

A

RNA and protein stability and lifetime

69
Q

can be regulated
by sequences in the untranslated regions

A

mRNA stability and translation

70
Q

Nucleotide sequences in the untranslated regions of mRNA contain

A

binding sites for proteins involved in RNA degradation

71
Q

In prokaryotes, the ribosome-binding site is a common target of

A

regulation

72
Q

control the expression of
thousands of genes

A

miRNAs

73
Q

miRNAs are packaged with
specialized proteins to form a

A

RISC complex

74
Q

RISC stands for

A

RNA-induced
silencing complex

75
Q

miRNAs base-pair with

A

mRNAs with complementary
sequences

76
Q

Once an mRNA base-pairs
with a miRNA, it is

A

degraded or translation is blocked

77
Q

destroy foreign
RNAs through RNA interference

A

siRNA

78
Q

eukaryotic protein complex capable of degrading damaged,
misfolded or un-needed proteins

A

Proteasome

79
Q

a small protein tag, gets covalently attached to of the target protein

A

Ubiquitin

80
Q

Ubiquitinated proteins are degraded by

A

proteases

81
Q

When the concentration of tryptophan inside the cell is high:

(a) the tryptophan repressor is activated
(b) the tryptophan repressor is inactivated

AND therefore…

(c) transcription of the tryptophan operon is allowed (d) transcription of the tryptophan operon is shut down

A

A, d

82
Q

In which conditions will the lac operon be switched ON?

A

Glucose absent, lactose present; CAP activator is bound to cAMP, lac repressor bound to allolactose

Cell Bio (15 decks)

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