7.2 Transcription and Gene expression (HL)

Question 1

What are the 3 main parts of transcribed RNA?

Answer 1

Promoter
Coding sequence
Terminator

Question 2

What is the function of the promoter?

Answer 2

Non-coding sequence responsible for initiation if transcription

Question 3

What binds the the promoter?

Answer 3

RNA polymerase

Question 4

What controls the binding of RNA polymerase to the promoter?

Answer 4

Transcription factors

Question 5

What are the two types of transcription factors?

Answer 5

Proximal or distal

Question 6

What is the function of the coding sequence?

Answer 6

To code for proteins

Question 7

What is the function of the terminator?

Answer 7

To stop RNA polymerase from continuing to transcribe

Question 8

Which strand is the antisense strand?

Answer 8

The strand that is transcribed into RNA

Question 9

Which strand is the sense strand?

Answer 9

The strand that is not transcribed into RNA

Question 10

What is another name for the antisense strand?

Answer 10

Template strand

Question 11

In which direction is the sense strand?

Answer 11

It is gene specific as either strand could have a gene

Question 12

What is transcription?

Answer 12

The process by which DNA sequence (gene) is copied into complementary RNA sequence

Question 13

What enzyme carries out transcription?

Answer 13

RNA Polymerase

Question 14

Describe the process of transcription

Answer 14

RNA pol covalently binds nucleotide triphosphates (releasing 2 phosphates)
The 5’ phosphate links to the 3’-end

Question 15

In what direction does transcription occur?

Answer 15

5’ - 3’

Question 16

What must happen to the RNA sequence post-transcriptionally in eukaryotes?

Answer 16

Modification to the RNA sequence

Question 17

Define capping

Answer 17

Involves adding a methyl group to the 5’ end of RNA

Question 18

Why does capping occur?

Answer 18

To protect against degradation by exonucleases
Also used for recognition

Question 19

What are the 3 post-transcriptional events that occur to form mature mRNA?

Answer 19

Capping
Polyadenylation
Splicing

Question 20

Define polyadenylation

Answer 20

Adding a long chain of adenine nucleotides (poly-A tail) to the 3’ end of the transcript

Question 21

Why does polyadenylation occur?

Answer 21

Improves transcript stability and facilitates the export from the nucleus

Question 22

Define splicing

Answer 22

The removal of introns from RNA

Question 23

Why does splicing occur?

Answer 23

Introns do not code for proteins

Question 24

Define alternative splicing

Answer 24

The removal of exons that will result in the formation of different polypeptides from a single gene sequence

Question 25

What are the functions of the regulatory proteins?

Answer 25

Bind to DNA sequences outside of the promoter and interact with transcription factors

Question 26

Where do activator proteins bind?

Answer 26

Enhancer site

Question 27

What is the function of activator proteins?

Answer 27

Increase rates of transcription

Question 28

Where do repressor proteins bind?

Answer 28

Silencer sequences

Question 29

What is the function of repressor proteins?

Answer 29

Decrease rates of transcription

Question 30

What can cause changes in gene expression?

Answer 30

A variety of external and internal factors such as chemical signals

Question 31

What determines how tightly DNA is packaged?

Answer 31

The protruding tails on histone

Question 32

What can make DNA coil less tightly on a histone?

Answer 32

Adding an acetyl group to the tail, neutralising the charge on the histone

Question 33

Why would we want DNA to coil less tightly?

Answer 33

Ease of transcription

Question 34

What can make DNA coil more tightly on a histone?

Answer 34

Adding a methyl group to the tail, maintaining the positive charge

Question 35

Define heterochromatin

Answer 35

DNA which is supercoiled and not accessible for transcription

Question 36

Define euchromatin

Answer 36

DNA which is loosely packed and therefore accessible to the transcription machinery

Question 37

What effect will increased methylation have on gene expression?

Answer 37

Decrease gene expression (by preventing the binding of transcription factors)

Question 38

Define epigenetics

Answer 38

The study of changes in phenotype as a result of variations in gene expression levels

Question 39

What factors (other than genes) can effect epigenetics?

Answer 39

Environmental factors
E.g.:
Pathogens, diet, exposure