Bacteriology Lecture 05 Bacterial Genetics Regulation Of Gene Expression

Front 1

Define attenuation

Back 1

The regulation of transcription termination as a mechanism of control of gene expression of some bacteria

Front 2

Define attenuator

Back 2

The terminator sequence at which attenuation occurs

Front 3

Define autoregulation

Back 3

The control of the transcription of a gene by its own gene product

Front 4

Define CAP (catabolite activator protein), or CRP (cAMP receptor protein)

Back 4

A positive regulator protein activated by cyclic AMP and needed to initiate transcription of certain operons susceptible to catabolite repression in E. coli

Front 5

Define constitutive gene expression

Back 5

The continued expression of a gene that does not respond to regulation

Front 6

Define coordinate regulation

Back 6

A common control of a group of genes

Front 7

Define corepressor

Back 7

A small molecule which triggers the repression of transcription by binding to a repressor protein

Front 8

Define derepressed

Back 8

Synonymous with induced when describing the expression of a normal gene which is turned on, and with constitutive in describing the effect of a mutation

Front 9

Define diauxic growth

Back 9

Biophasic growth on a mixture of two carbon sources in which one carbon source is used up before the other one is mobilized

Front 10

Define endproduct feedback inhibition

Back 10

Inhibition of the activity of any enzyme which catalyzes an early step in the pathway by a product of the metabolic pathway

Front 11

Define hairpin

Back 11

A double-helical region formed by base pairing between adjacent (inverted) complementary sequences in a single strand of RNA or DNA

Front 12

Define inducer

Back 12

A small molecule that triggers gene transcription by binding to a regulatory protein

Front 13

Define induction

Back 13

Switching on transcription of genes when the substrate of the induced enzymes are present as a result of interaction of the inducer with the regulatory protein

Front 14

Define merodiploid

Back 14

An organism that is diploid for some but not all of its genes

Front 15

Define negative regulation

Back 15

Regulation mediated by factors that block or turn off transcription

Front 16

Define operator

Back 16

The site on DNA at which a repressor protein binds to prevent transcription from initiating at the adjacent promoter

Front 17

Define operon

Back 17

A unit of bacterial gene expression and regulation, including structural genes and control elements in DNA recognized by regulator gene products

Front 18

Define pleiotropic

Back 18

Affecting more than one (apparently unrelated) phenotypes

Front 19

Define polycistronic mRNA

Back 19

It includes coding regions representing more than one gene

Front 20

Define positive regulation

Back 20

Regulation mediated by a protein that is required for the activation of a transcription unit

Front 21

Define promoter

Back 21

A region of DNA involved in binding of DNA-dependent RNA polymerase to initiate transcription

Front 22

Define regulatory genes

Back 22

Encoded gene products that control the expression of other genes

Front 23

Define repression

Back 23

Inhibition of transcription (or rarely translation) by binding of repressor protein to specific site on DNA or RNA

Front 24

Define repressor protein

Back 24

Binds to operator on DNA to prevent transcription initiation

Front 25

Define signal transduction

Back 25

A system that passes a signal received by a receptor through a series of intermediate molecules until final regulatory molecules, such as transcription regulators, are modified in response to the signal

Front 26

Define SOS response

Back 26

The coordinate induction of many enzymes in E. coli, including repair activities, in response to irradiation or other damage to DNA; results from activation of protease activity by RecA to cleave LexA repressor

Front 27

Define terminator

Back 27

DNA sequence which causes RNA polymerase to terminate transcription

Front 28

Define uninducible

Back 28

Mutants that cannot be expressed at all

Front 29

What does enzyme induction or repression refer to

Back 29

The regulation of enzyme synthesis rather than enzyme activity

Front 30

Where is regulation of enzyme synthesis by repression or induction at

Back 30

The level of transcription initiation

Front 31

What induces the synthesis of degradative (catabolic) enzymes

Back 31

Substrate or substrate analog

Front 32

What represses the synthesis of biosyntheic (anabolic) enzymes

Back 32

The end product

Front 33

What are the components of the DNA-dependent RNA polymerase holoenzyme

Back 33

The core enzyme (alpha,alpha, Beta, Beta') and the sigma factor which governs the recognition of promoters by the holoenzyme

Front 34

What is the rho factor required for

Back 34

Transcription to terminate at certain (rho dependent) termination sites

Front 35

What genes are constitutively expressed

Back 35

Many genes encoding so called "house-keeping" functions. Transcription initiation of these genes is not regulated by accessory proteins

Front 36

How are genes negatively controlled

Back 36

Genes controlled negatively by repressor proteins are not transcribed due to the presence of the repressor proteins

Front 37

How are genes positively controlled

Back 37

Genes controlled positively by activator proteins require the presence of activator proteins in order to initiate transcription

Front 38

What does lacZ encode

Back 38

Beta-galactosidase, which hydrolyzes the bond between the lactose sugars

Front 39

What does lacY encode

Back 39

Beta-galactoside permease, which brings lactose into the cell

Front 40

What does lacA encode

Back 40

Beta-galactoside transacetylase (function unknown)

Front 41

How is repression of the lac operon relieved

Back 41

By the addition of an inducer that binds to the repressor protein, alters the conformation of the repressor, and thereby reduces the affinity of the repressor for the operator

Front 42

How is the synthesis of biosynthetic enzymes repressed

Back 42

By the presence of end product. The repressor protein is inactive in the absence of the end product effector

Front 43

What is required for initiation of transcription at the lac promoter

Back 43

cAMP together with cAMP receptor protein (CRP or CAP)

Front 44

In bacteria, where is the regulation of protein synthesis primarily

Back 44

At the level of transcription rather than translation

Front 45

What is the difference between end product repression of enzyme synthesis versus inhibition of enzyme activity

Back 45

Repression of enzyme synthesis is concerned with the economy in macromolecular synthesis. Inhibition of enzyme activity is concerned with the economy in metabolite synthesis

Front 46

What does transcription termination at the end of a cistron or an operon involve

Back 46

A termination sequence, RNA polymerase, and rho factor

Front 47

How does secondary structure of mRNA play an important role in attenuation

Back 47

The leader peptide is followed by a transcription termination sequence. The mRNA can have two alternative conformations based on binding to the leader peptide

Front 48

In translational control, what is the correct start codon in the mRNA preceded by

Back 48

The Shine-Dalgarno (SD) sequence. The SD site must be free for translation to occur

Front 49

What is the SOS repair pathway

Back 49

A repressor, encoded by the lexA gene, reduces expression of numerous genes involved in DNA repair. In reponse to DNA damage, the recA protein is activated, which cleaves the lexA repressor, allowing transcription of the repair proteins

Front 50

Besides the lexA repressor, what else does the recA protease cleave

Back 50

The lambda repressor, as well as repressors of several other lambda related phages

Front 51

What does the two-component signal transduction system consist of

Back 51

A sensor kinase in the membrane, and a Response regulator in the cytoplasm

Front 52

What is quorum sensing

Back 52

Defines an environmental sensing system that allows bacteria to monitor their own population density

Front 53

What signaling molecules do gram positive bacteria use for quorum sensing

Back 53

Peptides. Gram negative use Acyl homoserine lactones