Chapter 18.1-18.2

Question 1

Intinsic terminators

Answer 1

cause RNA pol to terminate transciption on its own

Question 2

extrinsic terminators

Answer 2

requires additional proteins - Rho proteins

Question 3

Prokaryotes mRNAs

Answer 3

have multiple ribosome binding sites (RBSs) and can thus direct the synthesis of several diffrent polypeptides

Question 4

Regulation of gene expression can occur at multiple stages:

Answer 4

-Transcription
*mRNA half life
*Translation initiation
*Protein stability or activity
Positive regulation = enhancement of RNA polymerase activity

Question 5

catabolic functions are induced by

Answer 5

the presence of substrate

Question 6

Anabolic functions are often repressed by

Answer 6

he presence of an end
product

Question 7

Lactose to isomerized to

Answer 7

Allolactose (inducer of the genes for lactose utization)

Question 8

inducible regulation

Answer 8

gene control where transcription occurs only in the presence of an inducer.

Question 9

repressible regulation

Answer 9

gene control where transcription occurs only in the absence of a repressor.

Question 10

operon

Answer 10

a unit of DNA composed of two or more genes transcribed as a polycistronic mRNA under the control of a single promoter and operator.

Question 11

lac operon

Answer 11

a single DNA unit in E. coli, composed of the lacZ, lacY, and lacA genes together with the promoter (P) and operator site (o), that enables the simultaneous regulation of the three structural genes in response to environmental changes.

Question 12

allosteric proteins

Answer 12

proteins that undergo reversible changes in conformation when bound to another molecule (an effector).

Question 13

Promotor of lac operon acts in

Answer 13

cis, affecting the expression of only downstream strucural lac genes on the same molecule

Question 14

repressor of lac operon acts in

Answer 14

trans that binds to operator

Question 15

lac operon translation

Answer 15

B-gal, permease, transacetylase

Question 16

Lac repressor protein (LacI)

Answer 16

allosteric

Question 17

IPTG

Answer 17

non-metabolizable analog of lactose and an inducer of lac operon

Question 18

lacZ

Answer 18

encodes B-galactosidase

Question 19

lacY

Answer 19

encodes Lac permease

Question 20

inability to break down lactose resulted from mutations in two genes

Answer 20

lacZ and lacY

Question 21

lacA

Answer 21

encodes a transacetylase enzyme that adds a acetyl (CH3CO) group to lactose and other sugars (not used for breakdown)

Question 22

lacI

Answer 22

loss of function mutation located near but not within the lac operon

Question 23

lacI produce

Answer 23

constitutive mutants or repressor

Question 24

constitutive mutants

Answer 24

strains in which certain gene products are made all the time, irrespective of environmental conditions.

Question 25

constitutive mutants can synthesize

Answer 25

B-gal and Lac permease even in the absense of lactose

Question 26

repressor

Answer 26

a type of transcription factor that can bind to specific cis-acting elements and thereby diminish or prevent transcription. Repressors bind operators in prokaryotes and enhancers (or CpG islands) in eukaryotes.

Question 27

Mutant operator Oc

Answer 27

Nucleotide sequence is change
Repressor cannot recognize and bind to operator. lac enzymes are synthesized constitutively

Question 28

lacIS mutant

Answer 28

results in no expression of the Lac operon, even
in the presence of Lactose

Question 29

PaJaMo experiment

Answer 29

Transfer of the F’ (episome) during conjugation can
generate a “merodiploid” (partially diploid)

Question 30

LacI+ protein acts

Answer 30

in trans and is dominant to lacI-

Question 31

As a general principle of gene regulation through operons, regulatory genes encode

Answer 31

trans-acting proteins that interact with cis-acting DNA elements

Question 32

LacI binds to the

Answer 32

lac operator DNA

Question 33

DNaseI foot printing assay

Answer 33

To find the binding site for the
repressor

Question 34

catabolite repression

Answer 34

the repression of transcription in sugar-metabolizing operons like the lac operon when glucose or another preferred catabolite is present.

Question 35

cAMP regulatory protein (CRP)

Answer 35

can bind to the lac promoter region to allow max transciption only in the absense of glucose, when cAMP levels are high