Gene Structure In Prokaryotes

Question 1

Difference between Pro vs Eu mRNA

Answer 1

Pro have no caps at end, no premRNA and no splicing

Question 2

Promoter

Answer 2

It is a region of DNA where a polymerase will bind to start transcription

Question 3

Operator

Answer 3

It is the binding site for activators or inhibitors

Question 4

Operons

Answer 4

• It is a group of structural genes plus sequences that contrail transcription
  -Consist of promoter, Operator, and structural genes that will undergo transcription

Question 5

How do operons work

Answer 5

-A separate regulator with its own promoter encodes a regulator protein
-Regulator protein binds to operator site of operant to regulate transcription of premRNA
-Translation of mRNA leads to protein synthesis

Question 6

Types of operons

Answer 6

Negative inducible
Positive inducible
Negative repressive
Positive repressible

Question 7

Negative inducible operon

Answer 7

-Repressor regulator protein
-Ground state: transcription is OFF
-Transcription is activated when a small molecule (inducer) binds to repressor and makes it unable to bind to the operator
-Pathway is controlled by biodegradative pathways
-Chemical nature of the small molecule is an inducer

Question 8

Inducer

Answer 8

A substrate molecule for the enzymes encoded by the operon

Question 9

Positive Inducer

Answer 9

-Regulator protein is an activator
-transcription is OFF at ground state
-Τranscription is activated when a the inducer binds to the activator and enables it to bind to the operator and activate the operon expression
-Biodegradative pathway controls it
-Chemicla nature of small molecule is an inducer

Question 10

Negative (trick)

Answer 10

Protein that regulates it is a repressor

Question 11

Inducible (trick)

Answer 11

Operon is usually off

Question 12

Difference between activator and repressor

Answer 12

When activator is bound transcription occurs but only when repressor is not bound does transcription occur

Question 13

Negative repressible operon

Answer 13

-the regulator protein is a repressor
-Transcription is ON in ground state
-Transcription is repressed when a co-repressor binds to the repressor and enable it to turn off the operon transcription
-Biosynthetic pathways control this process
-Chemical nature of small molecule is a co-repressor
- By default the repressor protein is inactive and the co-repressor that binds to it making it active and able to bind to the operator to prevent the RNA Pol from binding to it is produced from enzymes that are encoded in the structural gene of the operon.

Question 14

Co-repressor

Answer 14

Product of the metabolic pathway catalyzed ( created) by enzymes encoded in the operon

Question 15

Positive repressible

Answer 15

-The regulator protein is an activator
-Transcription is ON in the ground state
-Transcription is repressed when a small molecule binds to the activator and its conformation is changed in such a way that it can no longer bind to the operator
-it is controlled by BIosynthetic pathways
-product big the metabolic pathway catalysed by enzymes encoded by the operon

Question 16

Riboswitches

Answer 16

-some regions are complementary in the RNA that cause them to bind together forming a riboswitch when stabilized by a regulatory protein
-The secondary structure that is stabilized masks a ribosome-binding site
-When the regulatory protein is removed, the riboswitch assumes an alternative secondary structure that makes the ribosome-binding site available
-This allows translation to take place

Question 17

Lactose metabolism in E.coli

Answer 17

Question 18

Lactose operon

Answer 18

Question 19

Writing out mRNA strand using template strand

Answer 19

-convert to coding strand
-reverse order
-replace T with U (mRNA)