Prokaryotic Genes

Question 1

What is a gene?

Answer 1

Segment of DNA that encodes information for a protein or functional RNA, as a linear sequence of nucleotides.

Question 2

What are the two major components of a typical gene?

Answer 2

1. Information to make functional protein or RNA
2. Information to control when it makes the protein/RNA it codes for.

Question 3

Why is it important there are mechanisms to control genes?

Answer 3

Don’t want cellular products to be produced all the time without control;
Can turn them on/off in response to cellular events;
Adjust the amount of product made by each gene

Question 4

What is the promoter element of a gene?

Answer 4

Regulates gene expression (when and how much a gene gets used)

Question 5

Where is the promoter element located on a gene?

Answer 5

upstream (5’ end)

Question 6

What is the protein coding sequence (CDS)?

Answer 6

Contains the information to make the protein.

Question 7

Where is the CDS located?

Answer 7

Downstream from the promoter.

Question 8

What initiates transcription for prokaryotes?

Answer 8

RNA polymerase binding to promoter.

Question 9

Where does transcription begin in prokaryotic genes?

Answer 9

At the +1 transcription start site

Question 10

Which portion of the gene gets translated to a protein in prokaryotes?

Answer 10

The CDS

Question 11

What is the start codon in prokaryotes?

Answer 11

ATG/AUG

Question 12

What is the stop codon (typically) in prokaryotes?

Answer 12

TAA, TGA, TAG

Question 13

What are the 5’ and 3’ UTRs in prokaryotic genes?

Answer 13

The regions of mRNA which do not get translated at the 5’ and 3’ ends.

Question 14

What is the difference in transcription for genes that code for proteins as opposed to genes that code for functional RNAs in prokaryotes?

Answer 14

RNA is made directly from transcription. The RNA may get post-transcriptionally modified but no translation occurs as protein CDS and UTRs do not exist.

Question 15

What is the main function of the prokaryotic promoter?

Answer 15

Attract RNA polymerase

Question 16

What are the three elements typically found in the prokaryotic promoter element?

Answer 16

UP element, -35 element, -10 element

Question 17

What is the consensus -35 element in the prokaryotic promoter?

Answer 17

TTGACA

Question 18

What is the consensus -10 element in the prokaryotic promoter?

Answer 18

TATAAT

Question 19

What is a consensus sequence?

Answer 19

Sequence of a conserved genetic element representing the most frequently occurring nucleotide at each position.

Question 20

What nucleotide base is usually the start site in prokaryotic transcription?

Answer 20

A

Question 21

How do you identify the transcription start site in prokaryotic genes?

Answer 21

Count from the middle of the -10 element.

Question 22

What does the relative position of -10 and -35 do?

Answer 22

Tells RNA polymerase which way to go.

Question 23

In which direction does RNA polymerase move along a prokaryotic gene?

Answer 23

From 5’ to 3’ on the coding/non-template strand.

Question 24

What is the coding strand in transcription?

Answer 24

The strand that the mRNA will be an exact copy of.

Question 25

What is the template strand in transcription?

Answer 25

The strand that RNA polymerase moves along and uses as a base pairing template.

Question 26

How does transcription begin?

Answer 26

RNA polymerase binds to -35 and -10 elements and unwinds DNA.

Question 27

In which direction is the mRNA assembled?

Answer 27

5’ to 3’

Question 28

Can genes be coded for on only one strand?

Answer 28

Can be coded for on either side; depends on the particular gene.