Regulation of Transcription and Translation

Question 1

What are transcription factors?

Answer 1

A transcription factor is a protein that controls the transcription of genes by binding to a specific region of DNA.

Question 2

Why are transcription factors needed?

Answer 2

They ensure that genes are being expressed in the correct cells, at the correct time and to the right level

Question 3

Give 3 reasons why transcription is regulated.

Answer 3

To direct cell division, growth and death
To direct cell migration and organisation during embryonic development
Allow cells to respond to external signals

Question 4

What is the 1st section of DNA involved in protein synthesis called?

Answer 4

Transcription unit

Question 5

What does ‘upstream’ mean?

Answer 5

The DNA before the start of the coding region.

Question 6

What 2 things bind to the promoter region in DNA?

Answer 6

RNA polymerase
Transcription factors

Question 7

What direction is DNA transcribed in to produce mRNA?

Answer 7

5’ to 3’

Question 8

What direction is DNA translated in to produce mRNA?

Answer 8

3’ to 5’

Question 9

Explain the role of the promoter region in transcription.

Answer 9

RNA polymerase binds and 2 strands of the structural gene will unwind and unzip from the site of the polymerase binding.

Question 10

Is the template or coding strand involved in transcription?

Answer 10

Template

Question 11

What biomolecule are transcription factors made from?

Answer 11

Proteins

Question 12

How do transcription factors enter the cell cytoplasm?

Answer 12

Through nuclear pores.

Question 13

Where do transcription factors bind to on the gene?

Answer 13

Promoter region

Question 14

What can transcription factors either cause or prevent?
How do they do this?

Answer 14

Transcription from taking place.
Transcription factors interact with RNA polymerase, either by assisting RNA polymerase binding to the gene (to stimulate expression of the gene) or by preventing it from binding (to inhibit gene expression)

Question 15

What are steroid hormones?

Answer 15

Small hydrophobic lipid based hormones that can pass directly into the nucleus through nuclear pores.

Question 16

Name the hormone that can act as a transcription factor.

Answer 16

Oestrogen

Question 17

What are ligand binding domains?

Answer 17

Binding sites that allow the factor to be responsive to an activating ligand.

Question 18

1. Oestrogen stimulation pathway
   Describe how oestrogen enters the cell nucleus.

Answer 18

It diffuses through the cell cytoplasm and attaches enters the nucleus through pores.

Question 19

2. Oestrogen stimulation pathway
   In the nucleus, what does the oestrogen attach to? What does this do to the thing it binds to?

Answer 19

An oestrogen receptor site. Binding leads to the receptor changing shape.

Question 20

3. Oestrogen stimulation pathway
   What does the new shape of the oestrogen receptor allow the oestrogen to do?

Answer 20

Causes the oestrogen to detach and diffuse towards the gene being expressed.

Question 21

4. Oestrogen stimulation pathway
   How does RNA polymerase become stimulated?

Answer 21

The ERα oestrogen receptor binds to a cofactor which enables it to bind to the promoter region of the gene, stimulating RNA polymerase binding and gene transcription.

Question 22

Explain why steroid hormones can rapidly enter a cell by passing through its cell surface membrane.

Answer 22

They are lipid soluble.
They can diffuse through the phospholipid bilayer.

Question 23

In cell cytoplasms, steroid hormones such as testosterone can bind to specific androgen receptors. Explain why.

Answer 23

Testosterone has a highly specific tertiary structure and can therefore bind to the receptor as it is complimentary.

Question 24

Binding of testosterone to androgen receptors changes its shape. The androgen receptor can then enter the nucleus and stimulate gene expression. Suggest how.

Answer 24

Androgen receptors could act as a transcription factor by binding to the DNA promoter region. This stimulates RNA polymerase.