T3: Gene expression, the lac operon and epigenetics

Question 1

What two types of transcription factor are there

Answer 1

Activators - promote RNA polymerase to bind to the promoter region

Repressors - prevent RNA polymerase from binding to the promoter region

Question 2

Where does RNA polymerase bind to on DNA

Answer 2

Promoter region

Question 3

Where do TFs bind to

Answer 3

DNA near to the promoter region

Question 4

What are the parts of an operon

Answer 4

Regulatory gene
Promoter region
Operator region
Structural genes

Question 5

What do regulatory genes do in operons

Answer 5

Code for a repressor transcription factor

Question 6

What does the operator region do in an operon

Answer 6

The location where TFs bind

Question 7

What does the promoter region do in an operon

Answer 7

Area where RNA polymerase binds to start transcription

Question 8

How do E.coli respire

Answer 8

Aerobically using glucose but can respire lactose in a lack of glucose

Question 9

What is the normal state of the lac operon

Answer 9

When glucose is being respired, repressor tfs bind to the operator to prevent RNA polymerase from binding so gene lac z, y and A are not expressed

Question 10

What happens with the lac operon when the E.coli needs to use lactose for respiration

Answer 10

Lactose binds to the lac I repressor gene which changes the shape of the repressor

This allows RNA polymerase to now bind to the promoter region

Genes lac z,y and A can now be transcribed to form mRNA and produce the proteins needed to respire lactose

Question 11

What is the link between gene combinations and plant flowering

Answer 11

The combination of genes expressed by a plant or parts of a plant determines which sturctures are formed

Question 12

What is methylation

Answer 12

The addition of methyl groups onto CpG sites

Question 13

What are CpG sites in DNA

Answer 13

Where a C base is next to a G base on the same strand

Question 14

What must you call acetylation in your answer

Answer 14

HISTONE MODIFICATION

Question 15

What does methylation do

Answer 15

Causes DNA to be more tightly wrapped around histones
Makes genes inaccessible - RNA polymerase can’t bind
So genes are not expressed

Question 16

What does histone modification do in terms of addition of acetyl groups

Answer 16

Causes DNA to be less tightly wound around histones
So genes are accessible for RNA polymerase to bind and for the gene to be transcribed

Question 17

Name some factors that affect epigentics

Answer 17

Smoking, alcohol diet and exercise

Question 18

What are oncogenes

Answer 18

Genes that code for proteins involved in the transition between phases in the cell cycle

Question 19

What are proto-oncogenes

Answer 19

The result of mutations to oncogenes

Question 20

What is the result of proto-oncogenes

Answer 20

The cell cycle can be continually active

Question 21

What are tumour suppressor genes

Answer 21

Genes that code for suppressor proteins that stop the cell cycle if there is a problem e.g gene mutation

Question 22

What can happen if tumour suppressor genes mutate

Answer 22

Cell cycle can be continually active

Question 23

What is the BRCA1 gene responsible for

Answer 23

Codes for proteins that repair damaged DNA

Question 24

What happens if someone has 1 faulty BRCA1 allele

Answer 24

If the other becomes damaged, there will be nothing to repair damaged DNA in the body.