chapter 36

Question 1

what is the template strand also called

Answer 1

antisense (-)

Question 2

what is the coding strand also called

Answer 2

sense (+)

Question 3

the antisense strand is complementary to

Answer 3

the sequence of the RNA transcript

Question 4

the sense strand of DNA has the same sequence as

Answer 4

the RNA transcript with T in place of U

Question 5

the first nucleotide to be transcribed is denoted

Answer 5

as +1

Question 6

the nucleotide immediately preceding the first nucleotide to be transcribed is denoted with

Answer 6

-1

Question 7

what is the role of σ subunit

Answer 7

identify promoters

Question 8

common promoters in E. coli are where

Answer 8

-10 sequence and -35 sequence, together called the core promoter

Question 9

what initiates transcription

Answer 9

RNA polymerase binds to promoter sites on the DNA template

Question 10

with is UP element

Answer 10

upstream promoter, located 40 to 60 nucleotides upstream from the start site

Question 11

what must happen to the DNA for transcription to occur

Answer 11

the DNA must be unwound

Question 12

how many base pairs need to be unwound

Answer 12

approx. 17 base pairs of DNA

Question 13

what is an intermediate in RNA synthesis

Answer 13

a DNA-RNA hybrid helix approx. 8 nucleotides in length

Question 14

transcription occurs at the rate of

Answer 14

50 nucleotides per second

Question 15

DNA replication occurs at the rate of

Answer 15

800 nucleotides per second

Question 16

elongation continues until

Answer 16

a termination signal (terminator) is detected

Question 17

the simplest stop signal is

Answer 17

a palindromic GC-rich region, which forms a hairpin structure pausing the RNA polymerase, and followed by multiple U for easy dissociation

Question 18

what does rho do

Answer 18

termination signal that binds to a particular sequence on the RNA product and uses the energy of ATP hydrolysis to chase down the polymerase in the transcription bubble

contact with rho causes the transcription bubble to dissociate

Question 19

does RNA polymerase proofread its product

Answer 19

yes

Question 20

constitutively expressed genes are

Answer 20

those that are transcribed all of the time

Question 21

most gene regulation occurs at the level of

Answer 21

transcription

Question 22

what’s the most common way of regulating gene expression

Answer 22

DNA sequences (usually upstream) in the vicinity of the gene

DNA-binding proteins bind to these sequences and enhance or repress gene expression

Question 23

what regulatory system was one of the first to be elucidated

Answer 23

lac repressor system

Question 24

in the absence of lactose…….

Answer 24

the gene for β-galactosidase, which metabolizes lactose, is minimally transcribed

Question 24

in the presence of lactose…..

Answer 24

the genes for β-galactosidase as well as two other enzymes—a permease and thiogalactoside transacetylase—are expressed

Question 25

what are the DNA components of an operon

Answer 25

regulator gene, an operator, a promoter, structural genes

Question 25

in the lac operon, the regulatory gene encodes…..

Answer 25

a protein called the lac repressor that binds to the operator site in the absence of lactose and prevents promoter use and this transcription of the structural genes

Question 26

when lactose is present….

Answer 26

the small amount of β-galactosidase in the cell converts it to
galactose and glucose

Question 27

what is generated in a side reaction in the conversion of β-galactosidase to glucose

Answer 27

allolactose

Question 28

what is the inducer of the lac operon

Answer 28

allolactose

Question 29

upon binding allolactose, the lac repressor…….

Answer 29

undergoes a structural change that greatly reduces its affinity for DNA

Question 29

what happens after allolactose binds to the lac operon and a structural change is undergone

Answer 29

RNA polymerase binds to the promoter and transcribes the structural genes of the operon