Regulation of Gene Expression, Chapter 18

Question 1

Metabolic control

Answer 1

1) Adjusting the activity of metabolic enzymes
2) regulating genes that encode metabolic enzymes

allosteric regulation, tryp controls the amount of genes transcribed

Question 2

gene expression

Answer 2

producing a product from a gene

Question 3

E. Coli

Answer 3

a bacterium that can produce a protein or amino acid (like tryp) when it’s lacking in the environment and stop making it when it’s available in the environment

when tryp is available we synthesize it

Question 4

tryptophan

Answer 4

is readily available in the environment and is an amino acid needed by E. Coli

also acts as a corepressor

Question 5

operon

Answer 5

consists of a group of genes and regulatory elements, working together to control the expression of those genes

can be switched off by a repressor and a corepressor

Question 6

repressor

Answer 6

binds to the DNA of an operator, so it blocks the way

Question 7

corepressor

Answer 7

cooperates with a repressor to switch an operon off

Question 8

trp operon

Answer 8

is a group of genes that encode enzymes for the amino acid tryptophan

tryp, which E. coli uses to build proteins

Question 9

trp operon expressed

Answer 9

“on” when tryp levels are low

Question 10

trp operon repressed

Answer 10

“off” when tryp levels are high

Question 11

trp operon

Answer 11

promotor, operator, and five genes on DNA

Question 12

promotor

Answer 12

when RNA pol binds

which is an enzyme that synthesizes RNA from a DNA template

Question 13

operator

Answer 13

where a repressor binds

Question 14

five genes of trp operon

Answer 14

trpE, trpD, trpC, trpB, trpA

all transcribed into mRNA and translated

Question 15

trp repressor

Answer 15

only bind to DNA and blocks transcription when tryp is present. it attaches to the repressor molecules and changes their shape so they become active

acts as both a sensor (tryp) and a switch

Question 16

high/present tryptophan

Answer 16

operon off, repressor active, no transcription

Question 17

low/absent tryptophan

Answer 17

operon on, repressor inactive, trp operon transcribed by RNA pol

Question 18

repressible operon

Answer 18

is one that is usually off

Question 19

inducer

Answer 19

inactivates the repressor and turns on transcription

i.e., the lac operon

Question 20

lac operon

Answer 20

contains genes coding for enzymes in hydrolysis and metabolism of lactose