Gene Expression

Question 1

What is gene expression?

Answer 1

The flow of information from DNA to final product

Question 2

What are the possible final products of gene expression?

Answer 2

Proteins (most common)
RNA (can also be produced)

Question 3

How are bacterial genes organized?

Answer 3

They are in transcriptional units with single or multiple genes in an operon

Question 4

RNA Polymerase

Answer 4

An enzyme that transcribes genes in bacteria; 5 subunits + a sigma factor

Question 5

Sigma Factor

Answer 5

Recognises promotor sequences

Question 6

What do promoter sequences denote?

Answer 6

Indicate where transcription starts

Question 7

How does the promoter affect transcription?

Answer 7

It can increase or decrease transcription by affecting how strong the sigma binding becomes (stronger or weaker)

Question 8

T/F Bacteria have genes for multiple sigma factors that can recognise different promoters?

Answer 8

True

Question 9

Holoenzyme

Answer 9

RNA polymerase with a sigma factor

Question 10

What are the three stages of transcription?

Answer 10

Initiation
Elongation
Termination

Question 11

What happens in the initiation phase of transcription?

Answer 11

Begins with the holoenzyme binding to the promoter and opening DNA

Question 12

What happens in the elongation phase of transcription?

Answer 12

RNA polymerase extends the growing RNA strand

Question 13

What happens in the termination phase of transcription?

Answer 13

RNA polymerase reaches a termination sequence and releases from the DNA strand

Question 14

Rho dependent termination

Answer 14

Rho polymer is threaded onto the new RNA strand and moved towards the polymerase. Once contact between the Rho and polymerase is initiated, termination occurs

Question 15

Rho independent termination

Answer 15

Termination is influenced by NusA protein. Creates a hairpin loop and once RNA polymerase interacts with it termination occurs

Question 16

Rifampicin (drug)

Answer 16

Targets bacterial RNA polymerase & blocks RNA exit tunnel creating a bactericidal effect

Question 17

If the gene product is a protein…

Answer 17

The RNA produced in transcription is called mRNA

Question 18

Transfer RNA (tRNA)

Answer 18

have an anticodon on one end & a matching amino acid on the other

Question 19

What is the function of a ribosome?

Answer 19

It travels along the mRNA and brings the correct tRNA to form peptide bonds between the amino acids

Question 20

Three steps of translation

Answer 20

Initiation
Elongation
Termination

Question 21

Initiation stage of translation

Answer 21

Ribosome binds to mRNA @ the start codon

Question 22

Elongation stage of translation

Answer 22

tRNA brings the correct amino acid and forms the peptide bonds

Question 23

Termination stage of translation

Answer 23

Ribosome reaches a stop codon & release factors disassemble the complex

Question 24

Why is it possible for transcription and translation to be coupled?

Answer 24

because there is no nucleus

Question 25

T/F - Each gene in a polycistronic mRNA has the same binding site, and start + stop codons?

Answer 25

False - they all have their own binding sites and codons

Question 26

What structure do proteins get folded into when they exit the ribosome?

Answer 26

Tertiary structure

Question 27

What happens if a protein is not correctly folded?

Answer 27

It will be degraded by a protease and used for something else

Question 28

T/F - Genes can be regulated at any point in expression

Answer 28

True

Question 29

T/F - Making an enzyme from scratch is easier and more favorable for a cell

Answer 29

False - it is easier to import rather than create b/c it is energetically less expensive