Bacterial Replication and Transcription 5.2

Question 1

Transcription is the synthesis of? Requires?

Answer 1

RNA from DNA template
* requires the enzyme RNA polymerase
and a DNA template

Question 2

What are the three major types of RNA that are synthesized?

Answer 2

• messenger RNA (mRNA)
• transfer RNA (tRNA)
• ribosomal RNA (rRNA)

Question 3

Is a primer required to initiate RNA synthesis?

Answer 3

no

Question 4

Is a promoter required to initiate RNA synthesis?

Answer 4

yes

Question 5

Transcription is the sequential addition of nucleotide bases onto the ___ ends of growing chains

Answer 5

3’

Question 6

RNA polymerase recognition of promoter requires a?

Answer 6

sigma factor protein

Question 7

what is a sigma factor protein?

Answer 7

a DNA binding protein that recognizes nucleotide sequences of promoters

Question 8

What is needed for RNA polymerase to bind at the correct transcription start site?

Answer 8

recognition sequences

Question 9

Where are two highly conserved regions needed for recognition and transcription?

Answer 9

~10 and ~35 bases upstream from where RNA synthesis begins

Question 10

Termination of RNA synthesis is dependent upon?

Answer 10

the recognition of specific base sequences by the polymerase at a stem-loop structure in RNA

Question 11

Does a unit of transcription contain one or many genes? Explain this significance

Answer 11

more than one

• Transcription of several genes into a single mRNA molecule usually occurs in prokaryotes
• THEREFORE the mRNA may contain the information for more than one polypeptide= polycistronic message

Question 12

what is a polycistronic message?

Answer 12

1) has multiple translation start and stop sites
2) contains info for more than one polypeptide
3) common in bacterial and chloroplast mRNAs

Question 13

What 3 location can control of gene expression or product activity occur?

Answer 13

1) transcriptional level
2) transnational level
3) post transnational level

Question 14

Regulation at the transcriptional level is achieved by what 7 things?operos

Answer 14

1. Induction (coming into existance)
2. Repression (stopped from coming into existance)
3. Positive control
4. Global control/catabolite repression
5. Quorum sensing
6. Attenuation (translational control)
7. Two component signal transduction (cell signalling method)

Question 15

What gives transcriptional control at a promoter region?

Answer 15

certain proteins have to bind to DNA
*this occurs due to interactions between specific domains of the proteins and specific regions or motifs of the DNA molecule

Question 16

helix-turn-helix motif protein

Answer 16

DNA binding protein

*one helix binds to one strand, the 2nd helix to the other strand; allows for binding of nucrleotide sequences

Question 17

zinc finger motif

Answer 17

DNA binding protein

*a protein that binds a zinc ion as the protein’s zinc finger binds to DNA

Question 18

What is an operon?

Answer 18

regulatory region plus coding region

*Genes that are transcribed together from a single promoter

Question 19

In prokaryotes, genes involved in similar metabolic pathways are often linked to the same?

Answer 19

promoter to yield a polycistronic messenger RNA

Question 20

All genes linked to some promoter can be _____ or _____ simultaneously?

Answer 20

downregulated (repression) or upregulated (induction) simultaneously

Question 21

Repression occurs when?

Answer 21

a repressor protein binds to operator region of an operon

Question 22

Promoter region-site where _____ binds

Answer 22

RNA polymerase

Question 23

Repressor binds to ______ to prevent transcription

Answer 23

operator DNA

Question 24

How is the repressor capable of binding to an operator?

Answer 24

by a corepressor binding to thee repressor

Question 25

repressors contain _____ sites which the corepressor can bind to

Answer 25

allosteric sitres

Question 26

the corepressor is often an end product from an?

Answer 26

anabolic pathway

Question 27

What increases the affinity for operator DNA and a repressor?

Answer 27

the binding of a corepressor to the repressor

Question 28

What is the ultimate complex that prevents RNA polymerase from transcribing genes?

Answer 28

repressor/corepressor/operator complex

Question 29

What decreases the affinity for operator DNA and a repressor?

Answer 29

an inducer binding to repressor at allosteric site changes conformation of repressor decreasing its affinity for operator DNA

Question 30

In case of Lactose operon, what is the inducer? derived from?

Answer 30

allolactose

*derived from lactose (via beta-galactosidase) that needs to be catabolized by the bacterial cell