RNA Synthesis & control in Bacteria

Question 1

Copying DNA base sequence by replicating into RNA format

Answer 1

Transcription - pre-mRNA

Question 2

General nature of Transcription

Answer 2

DNA to RNA TO Protein

Question 3

Does transcription of the whole genome occur during RNA synthesis?

Answer 3

No, only a section of dsDNA is transcripted to form a ssRNA.

Question 4

What controls which genes are transcribed where and when?

Answer 4

Regulatory elements such as terminal and start sequence of bases found in the DNA generally control this element.

Question 5

Region of DNA that leads to initiation of particular gene

Answer 5

Promoter region

Question 6

Strand of DNA that holds the information.

Answer 6

Non-template strand or coding strand.

Question 7

Which strand is copied to receive the same information as the coding strand?

Answer 7

The template strand. By producing RNA from this strand allows complementary base pairing to form the same information as the coding strand which is required to form polymers of RNA.

Question 8

Uracil is only found in RNA

Answer 8

Yes, RNA uses Uracil in place of Thymine in RNA strands.

Question 9

Which way does RNA transcription occur?

Answer 9

An RNA strand is synthesized in the 5’ to 3’ direction. The template strand is followed in the 3’ to 5’ direction.

Question 10

In prokaryotes transcription is catalysed by…

Answer 10

a single RNA polymerase. It can also unwind DNA.

Question 11

Three main types of RNA found in bacteria and eukaryotes?

Answer 11

• Messenger RNA (mRNA)
• Transfer RNA (tRNA)
• Ribosomal RNA (rRNA)

Question 12

Along with the three main types of RNA found, which additional type of RNA found in which species?

Answer 12

snRNA - small nuclear RNA

microRNA and siRNA.

Found in eukaryotes only.

Question 13

What are the RNA molecules that are known to help regulate the translation of RNA?

Answer 13

microRNA and siRNA (Short interfering)

Question 14

Role in RNA processing?

Answer 14

snRNA. This is found only in eukaryotes along with the regulatory molecules.

Question 15

3 important regions in bacterial structural genes

Answer 15

1. Promoter region
2. Coding region
3. Termination sequence

Question 16

When the promoter region and termination sequences are translated, what does this result in the pre-mRNA?

Answer 16

Leadeer/trailer sequence which are untranslated.

Spliced from the strand to become mRNA

Question 17

What is the significance of the -35 sequence and -10 sequence found in E. coli DNA?

Answer 17

Critical for specifying the initiation of transcription.

Question 18

Where are the -35 and -10 sequences found?

Answer 18

Before the start of transcription (no. of bp away)

Question 19

Enzyme that binds to promoter region to begin transcription

Answer 19

RNA polymerase holoenzyme

Question 20

Holoenzyme is made up of 4 subunits. What are they?

Answer 20

Two a, b and b’

Sigma factor - essential for recogintion of promoter sequence.

Question 21

Binding of RNA polymerase leads to…

Answer 21

1. RNA polymerase loosely binds to -35 sequence
2. Tighter binding around -10 sequence leads to untwisting of DNA into ssDNA
3. High A/T content helps with forkming ssDNA

Question 22

Recognition of termination comes from…

Answer 22

RNA polymerase recognising signals for chain termination.

Leads to:

• Release of RNA chain
• Release of enzyme from the template strand.

Question 23

Why do RNA strand that are being synthesized form hairpin loops?

Answer 23

Regions of complementary sequence within the RNA molecule produce antiparallel double stranded RNA regions separated by unpaired segments of RNA – forms “loops”

Hairpin loop forms which marks termination of transcription.