2E: Gene Regulation

Question 1

Gene Regulation

Answer 1

the control of gene expression to conserve energy, achieved by switching transcription on or off

Question 2

Gene Expression

Answer 2

the process of reading the information stored within a gene to create a protein

• involves structural and regulatory genes

Question 3

Structural Gene

Answer 3

responsible for producing proteins that are involved in the structure or function of a cell

e.g. may code for enzymes, transport, proteins, receptors

Question 4

Regulatory Gene

Answer 4

responsible for the production of regulatory proteins

i.e. either repressor or activator proteins

• can produce many different proteins by producing factors which result in exons being combined in different ways(alternative splicing)

Question 5

Regulatory Proteins

Answer 5

responsible for either:
- turn gene expression off or on,
- or increase or decrease the rate of gene expression

• also can control types of post-transcription modifications

Question 6

Repressor proteins

Answer 6

inhibit or decrease the expression of structural genes

Question 7

Activator proteins

Answer 7

initiates or increases the expression of structural genes

Question 8

Operon

Answer 8

a cluster of linked genes that all share a common promoter and operator and are transcribed at the same time

Question 9

Conformational Change

Answer 9

a change in the 3D shape of a macromolecule such as a protein

Question 10

What is the Trp Operon

Answer 10

a series of genes that are involved in the production of the amino acid tryptophan, which can subsequently be used in protein production.

Question 11

What is Trp Operon made of

Answer 11

is composed of a series of structural genes which are controlled by a common promoter and operator. The entire trp operon is then composed by a regulatory gene located upstream

Question 12

Tryptophan

Answer 12

a building block for large and complex proteins

Question 13

What occurs when high levels of Tryptophan are free in the cytosol

Answer 13

1. When high levels of tryptophan are present, it binds to the repressor protein inducing a conformation change in the repressor protein
2. This then allows the repressor protein to bind to the operator region allowing the repressor protein to prevent transcription of structural genes by blocking RNA polymerase(inhibiting tryptophan production)

Question 14

What occurs when low levels of free tryptophan are present in the cytosol

Answer 14

1. When low levels of tryptophan are present, there is an insufficient quantity of tryptophan molecules to bind to the repressor protein.
2. This causes the repressor protein to de-attach from the operator region allowing RNA polymerase to transcribe the trp structural gene so that the level of tryptophan can increase

Question 15

Attenuator region

Answer 15

A regulatory feature found throughout prokaryotes causing premature termination of transciption.

• Contains a high concentration of Adenine and Uracil, only two hydrogen bonds present (relatively weaker than C-G).
• Allows it to be more easily pulled away due to two hydrogen bonds stoping RNA polymerase