Chap 7- Sensing & Responding to Environments

Question 1

Due to changing environments, microorganisms to be very ______ to survive

Answer 1

adaptable

Question 2

Process that transmits info from outside a cell to the inside; allows cell to respond to changing environments

Answer 2

signal transduction

Question 3

ability to sense density of other cells in their own population

Answer 3

quorum sensing (few cells present, signaling molecule is low; lots of cells present, signaling molecule is high)

Question 4

How does natural selection play a role in gene expression?

Answer 4

enhances survival of at least part of population

Question 5

alteration of characteristics of surface proteins; Allows pathogens to stay step ahead of host defenses

Answer 5

antigenic variation

Question 6

involves switching genes on and off

Answer 6

phase variation

Question 7

biological process of first the transcription of DNA into RNA (mRNA) and then translation of that mRNA into protein, so protein can carry out its function

Answer 7

expression

Question 8

genes that are synthesized constantly

Answer 8

constitutive genes

Question 9

genes Turned on only when needed

Answer 9

inducible genes

Question 10

genes constantly produced; Turned off only when theyre not needed

Answer 10

repressible genes

Question 11

regulatory Protein that blocks transcription of a gene

Answer 11

repressor

Question 12

regulatory mechanism that turns on (induces) the transcription of a gene

Answer 12

Induction; turned on by an INDUCER

Question 13

If inducer is absent, gene expression is turned ______

Answer 13

off

Question 14

regulatory mechanism that inhibits (represses) the transcription of a gene

Answer 14

Repression (handles by COREPRESSORS)

Question 15

How does repressor block transcription?

Answer 15

Repressor binds to operating site on DNA, which does not allow RNA Polymerase to advance past the DNA sequence (operator) stopping transcription

Question 16

How does repressor work in induction?

Answer 16

Repressor is synthesized in a form that can bind to operator, so TRANSCRIPTION IS OFF!!! Inducer attaches to repressor, changing repressor’s shape & function (can no longer attach to operator) now Repressor cannot bind to DNA and RNA polymerase can transcribe gene

Question 17

How does repressor work in repression?

Answer 17

Repressor is synthesized in a form that cannot bind to operator, SO TRANSCRIPTION IS ON!!! Now a corepressor is needed. Corepressor-repressor complex is formed & binds to operator blocking transcription.

Question 18

Group of linked genes whose expression is controlled as a single regulatory signal

Answer 18

operon

Question 19

Two regions of an operon

Answer 19

control region + structural genes

Question 20

Control region is broken into 2 parts. (_______ )where RNA polymerase binds to DNA to START transcription. 2nd part is (_________) where repressor binds to DNA to INHIBIT transcription

Answer 20

promoter; operator

Question 21

Region of operon where genes are regulated by control region

Answer 21

structural genes

Question 22

If an inducer is present

Answer 22

repressor CANNOT bind to operator

Question 23

If inducer is absent, where is the repressor?

Answer 23

repressor is bound to operator

Question 24

Example of Inducible operon

Answer 24

LAC operon - all the enzymes to carry out lactose metabolism are encoded

Question 25

If co repressor is ABSENT

Answer 25

repressor CANNOT bind to operator

Question 26

If co repressor is PRESENT

Answer 26

repressor CAN bind to operator

Question 27

Example of Repressible Operon

Answer 27

Tryptophan, where EXCESS tryptophan is a co-repressor. WHEN IT IS ABSENT structural genes of this operon are continuously being transcribed and translated