Transcription, lac operon, arginine

Question 1

Describe - Transcription initiation

Answer 1

RNA polymerase binds to promoter region upstream of the gene

guided with sigma factor

Question 2

Describe - Transcription Elongation

Answer 2

RNA polymerase adds nucleotides complementary to the DNA template strand in the 5’ → 3’

(Uracil (U) is placed complementary to adenine (A)

Question 3

Describe - Transcription Termination

Answer 3

RNA polymerase recognizes a “STOP” sign in the DNA and releases the transcript (100-1,200 bases long)

Question 4

Translation list 5 stages

Answer 4

1. initiation
2. elongation
3. termination
4. protein folding
5. processing

Question 5

Transcription produces mRNA complementary to the

Answer 5

DNA gene

Question 6

During translation, tRNAs use their anticodon to interpret the ___ ____ and bring in the specific _____ ____

Answer 6

mRNA codons; amino acids

Question 7

What are two types of operon?

Answer 7

Inducible

Repressible

Question 8

Inducible

Answer 8

operon is turned ON by substrate: catabolic operons - enzymes needed to metabolize a nutrient are produced when needed

Question 9

Repressible

Answer 9

genes in a series are turned OFF by the product synthesized; anabolic operon –enzymes used to synthesize an amino acid stop being produced when they are not needed

Question 10

Many strains of Staphylococcus are now resistant to

Answer 10

pencillin

Question 11

One bacterial protein that confers penicillin resistance is called

Answer 11

beta-lactamase

Question 12

Beta-lactamase function

Answer 12

is an enzyme that cuts up and deactivates penicillin

Question 13

Gene for beta-lactamase only expressed in the presence of

Answer 13

penicillin

Question 14

When the bacteria is not exposed to penicillin, that gene is turned off and what happens?

Answer 14

and no beta-lactamase is made

Question 15

Understanding how beta-lactamase gene is turned on/off, can help us to design a drug to disable that gene’s expression (turn off the gene) can lead to what

Answer 15

making penicillin-resistant strains of Staph again vulnerable to penicillin.

Question 16

What 3 segments of lactose operon is made of?

Answer 16

regulator
control locus
structural locus

Question 17

Operon

Answer 17

set of genes under the control of a single promoter

Question 18

Regulator codes for

Answer 18

gene that codes for repressor

Question 19

Control locus composed of

Answer 19

promoter and operator

Question 20

Structural locus made of 3 genes each coding for an enzyme needed to

Answer 20

catabolize lactose

Question 21

the enzymes needed to catabolize lactose

Answer 21

B - galactosidase
permease
beta-galactosidase transacetylase

Question 22

B - galactosidase function

Answer 22

hydrolyzes lactose

Question 23

Permease

Answer 23

brings lactose across cell membrane

Question 24

Beta-galactosidase transacetylase

Answer 24

uncertain function

Question 25

When would you need beta-galactosidase?

Answer 25

• when lactose is in the environment
• so it would be useful for lac operon - to give bacteria the ability to control transcription of translation of permease and galactosidase

Question 26

when is the lac operon is OFF? (think about glucose)

Answer 26

normal -> glucose presenst

Question 27

glucose is the primary precursor of

Answer 27

lactose

Question 28

when is lac operon ON? Think about glucose

Answer 28

no glucose

Question 29

Describes what opens when lac operon off?

Answer 29

NO LACTOSE

In the absence of lactose, a repressor protein (the product of a regulatory gene located elsewhere) attaches to the operator of the operon. This effectively blocks transcription of structural genes downstream (to its right). Suppression of transcription (and translation) prevents the unnecessary synthesis of enzymes for processing lactose.

Question 30

Is arginine operon inducible or repressible?

Answer 30

repressible

Question 31

is lac operon inducible or pressible?

Answer 31

inducible

Question 32

is the arginine operon normally on or off?

Answer 32

ON

Normally on and will be turned off when the product of the pathway is no longer required.

Question 33

is the lac operon on normally on or off?

Answer 33

off

Question 34

Describe when operon is on for arginine?

Answer 34

A repressible operon remains on when its nutrient products (here, arginine) are in great demand by the cell. The repressor has the wrong shape to bind to the DNA operator without a corepressor, so that RNA polymerase is free to actively transcribe the genes and translation actively proceeds.

Question 35

Describe when excess arginine is present

arginine is a ________

Answer 35

When excess arginine is present, it binds to the repressor and changes it. Then the repressor binds to the operator and blocks arginine synthesis. Arginine is the corepressor

Question 36

describe operon off for arginine

Answer 36

1. Operon Off: Arginine building up

The operon is repressed when (1) arginine builds up and, serving as a corepressor, activates the repressor. (2) The activated repressor complex affixes to the operator and blocks the RNA polymerase and further transcription of genes for arginine synthesis.