Transcription (Bacteria)

Question 1

What is transcription?

Answer 1

Process by which information in a strand of DNA is copied into messenger RNA (mRNA)

Question 2

How is RNA synthesized?

Answer 2

Catalyzed by RNA polymerase

Question 3

What is sense DNA strand?

Answer 3

Same side of mRNA

Question 4

What are promoters?

Answer 4

DNA sequences that lie “upstream” of gene

Question 5

What are promoter sequences?

Answer 5

Sequences are recognised by RNA polymerase and tells RNA pol. where to start transcribing DNA into RNA

Question 6

True or false: Is the sequence of the sense DNA strand is sequence of the mRNA transcript?

Answer 6

True. mRNA synthesizes the top strand/coding strand/sense strand and replaces T with U

Question 7

What are the three stages of DNA-directed RNA synthesis transcription?

Answer 7

1. Initiation
2. Elongation
3. Termination

Question 8

Describe the initiation process

Answer 8

RNA pol. recognizes and binds to promoter sequence on DNA
RNA pol. unwinds DNA template

Question 9

What does RNA polymerase do on promoter?

Answer 9

Sits on promoter and melts the strands “off” each other

Question 10

Describe the elongation process

Answer 10

RNA pol. elongates new RNA molecule
Nucleotides are added
Substrates, ribonucleoside triphosphates are hydrolyzed

Question 11

Describe the termination process

Answer 11

Special DNA sequences terminate transcription
RNA pol. is released from DNA and free to initiate transcription again

Question 12

What is the coding sequence?

Answer 12

Region of transcript that is translated

Question 13

What is RNA polymerase?

Answer 13

Large multi-protein complexes
Homodimer and heterodimer subunits

Question 14

What does transcription require?

Answer 14

Requires specific sequences in template DNA to direct and modify RNA polymerase activity

Question 15

What do regulatory proteins do?

Answer 15

Bind within region of transcription start point and act to increase or decrease polymerase activity

Question 16

What recognizes promoter sequence?

Answer 16

RNA pol. cannot bind to promoter sequence
Sigma factors bind to two sequences

Question 17

Give an overview of transcription in prokaryotes

Answer 17

Core enzyme forms complex with sigma factors
Enzyme forms a complex with promoter
DNA is unwound
RNA synthesis begins by adding rNTPs
Sigma factors dissociates
RNA synthesis continues

Question 18

What is the common transcription terminator?

Answer 18

Hairpin loop which is formed by complementary sequence with RNA

Question 19

How does hairpin loop interfere with transcription?

Answer 19

Destabilized process by interfering with enzyme active site

Question 20

What are operons?

Answer 20

Clusters of co-regulated genes involved in same process and transcribed onto single polycistronic mRNA