6.4 Regulation of Gene Expression (CQ - exam)

Question 1

What are constitutive genes and wiring important for cell survival?

Answer 1

Constitutive genes are genes that are turned on all the time and critical for life and cell function.

Question 2

How is cell specialization possible when all of the cells in an organism contain the same genetic information?

Answer 2

each cell has a different set of active genes. The patterns of active genes influence their cell specialization.

Question 3

Explain how the lac operon is an inducible operon.

Answer 3

it is inactive until turned on. Lac operon’s inducer is lactose, without it, there is no purpose because there is nothing for it to break down.

Question 4

What is a transcription factor?

Answer 4

Proteins that switch genes on helping RNA polymerase bind.

Question 5

operon vs operator

Answer 5

operon is a cluster of genes controlled by a nearby promoter

Operator is a sequence of DNA in the regulatory region to which repressor proteins bind

Question 6

activator vs repressor

Answer 6

Activator is determines how fast the genes are transcribed.

Repressor is a protein that binds to the operator to inhibit transcription initiation

Question 7

Describe how each of the following conditions would affect the transcription of lactose metabolizing enzymes by the lac operon: high levels of lactose

Answer 7

Transcription occur due to inducer

Question 8

Describe how each of the following conditions would affect the transcription of lactose metabolizing enzymes by the lac operon: no lactose

Answer 8

No transcription because no inducer

Question 9

Describe how each of the following conditions would affect the transcription of lactose metabolizing enzymes by the lac operon: high levels of lactose and the absence of activator protein

Answer 9

• No binding cap and repressor
• Activator speeds up
• Transcription will occur but slowed

Question 10

Describe how each of the following conditions would affect the transcription of lactose metabolizing enzymes by the lac operon: no lactose and the absence of activator protein

Answer 10

No transcription, no inducer

Question 11

How does the trp operon differ from the Lac operon?

Answer 11

The trp operon is active unless turned off and the lac operon is inactive unless turned on with the presence of lactose.

Question 12

What is the role of activators in transcriptional control? Are they necessary for transcription?

Answer 12

Activators act as catalysts to the transcriptional control process. They are not necessary, they are there to bind and speed up the rate. Without an activator, it would be at a extremely slow rate.

Question 13

process of RNA interference.

Answer 13

RNA interference is a small RNA molecule that can control translation.

Question 14

what will happen to a primary transcript that lacks a poly-A tail or a 5’ cap. How will this affect translation?

Answer 14

• it will not be recognized by translation machinery.
• leaves mRNA vulnerable to degradation by enzyme.

Question 15

process of gene regulation differs between prokaryotic and eukaryotic cells.

Answer 15

Prokaryotes
- Does gene regulation during transcription, translation, and after protein synthesis
- Uses operons

Eukaryotes
- Does gene regulation during pre-transcriptional control, transcriptional control, post-transcriptional control, translational control, and post-translational control
- No operons

Question 16

five levels of eukaryotic gene regulation in the cell

Answer 16

1. Pre-transcriptional control
   - Chromatin modifications are met: acetyl group added to histones and DNA is methylated
2. Transcriptional control
   - transcriptional factors and activators
3. Post-transcriptional control
   - mRNA uses a protein chaperon to exit nucleus - - and RNA interference
4. Translational control
   - Ensuring cap and tail
5. Post-translational control
   - Modified to add phosphate, remove amino acid, and adding sugar or lipid

Question 17

What is the importance of regulating gene expression?

Answer 17

Regulating gene expression is a cell controlling which genes are expressed. This is essential for cell functions to be properly carried out.