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Genetics > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

Operons

A
  • groups of genes that are transcribed as a unit

-genes expressed in bacteria is often regulated through

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2
Q

Why is gene regulation necessary?

A
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3
Q

What are the differences between genes and regulatory
elements?

A

Regulatory genes code for proteins that affect transcription, while regulatory elements are the DNA sequences where those proteins bind to

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4
Q

How is gene expression controlled?

A
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5
Q

How can ecoli make what it needs when not given what it needs, and alter its own biochemistry?

A

Gene regulation
it decides and controls when to turn on what breaks down glucose

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6
Q

if enviorment changes…

A

new genes
expressed, new proteins synthesized!

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7
Q

gene expression is critical to all living things….

A

because it enables the synthesis of functional gene products that ultimately affect a phenotype

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8
Q

Structual genes

A

encoding proteins for metabolism or biosynthesis to break things down or play structural role in cell

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9
Q

Regulatory genes

A

regulating the expression (on and off button)

interacts with other
DNA sequences affect the transcription
translation of sequences.

Bacteria and eukaryotes use to control expression of many structural genes.

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10
Q

constitutive genes

A

expressed continually, not regulated

“Housekeeping genes”: integrity of cell, needs to keep turned on

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11
Q

Regulatory elements

A

DNA sequences not transcribed, regulating other nucleotide sequences

affecting expression of DNA sequences at which they are
physically linked

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12
Q

Regulation can occur through: Positive control and Negative control

A

P: stimulate
gene expression

N: inhibit
gene expression
not nessicarlly bad can turn off cells that are beneficial when off

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13
Q

many different places where gene expression is controlled

A

cant access genes if wrapped tightly around histones and bubble cant open

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14
Q

gene regulation at transcription

A

cant make the amount of transcript product pre-mRNA that it needs

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15
Q

any stages that we modify

A

what kind of mRNA we get and affects gene expression

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16
Q

stability changes gene expression by

A

decreasing stability decreases ability to get to transcription stage and changes the amount of protein made

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17
Q

Regulatory proteins have domains (section of protein)

A
  • Typically consist of ~ 60-90 amino acids
  • Responsible for binding to DNA
  • Forming hydrogen bonds with DNA (bind dynamically: - transiently bind and unbind DNA and other
    regulatory proteins)
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18
Q

Much of the gene regulation is accomplished by

A

proteins that
bind to DNA sequences and affect their expression

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19
Q

Motifs**

A

DNA-binding proteins , group binding proteins based on the similarities

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20
Q

What is the difference between a structural gene
and a regulator gene?

A

Structural genes encode proteins; regulator genes
control the transcription of structural genes.

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21
Q

Two types of transcriptional control: Negative control and Positive control

A

N: – regulatory protein is a repressor,
binding to DNA and inhibiting transcription

P: – regulatory protein is an activator,
stimulating transcription

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22
Q

Operons can also be either inducible or repressible:

A

I –transcription is normally off (not taking
place). has ability to be turned on and off but has to have something to do turn on

R – transcription is normally on (taking
place); has ability to be turned on and off but has to have something to do turn off

23
Q

Regulator gene encodes an active repressor protein that binds to the operator.

A

This system is inducible because transcription is normally off
(inhibited) and must be turned on (induced).

In order to have transcription happen have an inducer bind to the opening to stop

– Binding of inducer changes shape & prevents DNA binding.

24
Q

allosteric
proteins

A

– Proteins that change shape due to binding

25
Negative Inducible operons
control proteins that carry out degradative processes – proteins that break down molecules The proteins are not needed unless the substrate (the component that needs to be broken down) is present!
26
Negative Repressible Operons
On and needs to be turned off Repressor synthesized in inactive form that can't immediately attach to operator need to activate it (done by Product U or corepressor)
27
If U levels are high...
it is available to bind to the repressor and activate it, preventing transcription
28
E coli binding
if glucose is available then used but, can use lactose as energy source but has to be brought into the cell by te permease
29
Economical Negative Repressible Operons:
The proteins they encode are synthesized only as needed! Usually control proteins that carry out the biosynthesis of molecules needed in the cell (such as amino acids). Usually turned on and only turned off when there are adequate amounts of product already present!
30
In positive transcriptional control...
– the regulatory protein involved is an activator. It binds to DNA (usually at a site other than the operator) and stimulates transcription.
31
CAP
(catabolite activator protein) site in the lac operon!
32
Lactose
major carbohydrate found in milk; does not easily diffuse across the membrane. Transported by a protein lactose permease.
33
To use lactose as an energy source, E. coli must
break it into glucose and galactose – a reaction catalyzed by β-galactosidase. Can also convert lactose to allolactose
34
Enzymes β-galactosidase
permease and transacetylase are encoded by adjacent structural genes in the lac operon and have a common promoter
35
coordinate induction
the simultaneous synthesis of several protein stimulated by a specific molecule, the inducer! Allolactose is responsible!
36
In the trp operon, what happens to the trp repressor in the absence of tryptophan?
It cannot bind to the regulator gene and transcription takes place
37
Ribozymes
mRNA molecules with catalytic activity
38
Riboswitches
molecules influence the formation of secondary structures in mRNA
39
Antisense RNA
RNA molecules that are complementary to particular sequences on mRNA control gene expression by binding to sequences on mRNA and inhibiting translation
40
Enhancer
DNA element that affects transcription but typically found some distance from the gene whose transcription it affects. Enhancers contain binding sites for proteins that increase the rate of transcription.
41
The repression of the lac operon never
completely shuts down transcription There is a very low level of transcription and molecule production (basal level of transcription) This is critical because a few molecules are necessary to covert some of the lactose into allolactose – which then induces transcription!
42
catabolite repression is when....
When glucose is available, genes that participate in the metabolism of other sugars are turned off… This is a positive control mechanism.
43
Catabolite repression:
using glucose when available and repressing the metabolite of other sugars. * activated by catabolite activator protein (CAP). * cAMP binds to CAP; together CAP–cAMP complex binds to a site slightly upstream from the lac gene promoter
44
cAMP:
adenosine-3′, 5′-cyclic monophosphate Derivative of ATP, used in many biological pathways [cAMP] is inversely proportional to the level of available glucose.
45
What is the difference between a structural gene and a regulator gene?
structural encodes for protein reg- encodes for tscript factors
46
In the presence of allolactose, the lac repressor _____.
cannot bind to opressor
47
What is the effect of high levels of glucose on the lac operon?
Little to none transcription takes place
48
* A negative repressible operon
(normally turned on and must be repressed when products of its structural genes are not needed).
49
five enzymes together convert chorismate to tryptophan
* Five structural genes * trpE, trpD, trpC, trpB, and trpA—
50
attenuation
transcription begins at the start site but terminates prematurely, before the RNA polymerase even reaches the structural genes
51
what is the difference between a structural gene and a regulator gene?
Regulator genes control the transcription of structural genes, while structural genes encode specific proteins.
52
Permease
create opening for lactose to enter so beta gala can do its thing to create gluc
53
Allolactose
binds to regulatory protein acts as corepessor and lets RNA poly do its thing
54
CAP/cAMP how it influences gene expression
when gluc. is high this is low vice versa "push" to RNA polymerase to go increases the system

Genetics (19 decks)

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