Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Molecular Biology > Lecture 11 Prokaryotic Gene Regulation > Flashcards

Lecture 11 Prokaryotic Gene Regulation Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is the Lac operon

A

Cluster of genes that code for beta galactosidase, permease and acetylase. 3 structural genes, Laz Z,Lac Y, Lac A. 1 upstream gene Lac ?/

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do the cluster of genes in the TRP operon do

A

they encode gees for the amino acid tryptophan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the two types of operon

A
  • Inducible

- Repressible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In which organisms are operons typically found

A

Prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What type of messenger RNA molecule is produced from an operon

A

Polycistronic mRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the result/phenotype of the Lac I- mutation

A
  • Lac I- mutation produces a faulty repressor molecule that cannot bind to the operator.
  • Lac operon is no longer inducible by lactose.
  • Beta galactosidase is continually expressed as lac operon is permanently switched on.
  • Lac I- mutation results in a permanently switched on ac operon, where Beta galactosidase is constantly expressed, independant of lactose concentration. It is known as a constitutive mutation.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the result/phenotype of the Lac O c mutation

A
  • Lac O c mutation is a mutation in the operator region.
  • ## It is a cis acting muation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define cis-acting element

A
  • Regulatory sequences that can only regulate DNA directly next to it/adjacent to it
  • Cis acting elements include promoters/enhancers/ silencers.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define trans-acting factor

A
  • Transcription protein factors usually

- Trans acting factors can regulare DNA sequences anywhere.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is meant by the term constitutive mutation

A

This is a mutation that results in the operon being permanently switched on.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Give an example of a constitutive mutation

A

the Lac I- mutation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is meant by trans acting mutation, and give an example

A
  • Lac I- mutation

- This is a mutation in a trans acting factor - the Lac Repressor molecule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is meant by a cis acting mutation and give an example

A
  • Lac O c mutation

- This is a mutation in a cis acting element, the operator region of the lac operon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Explain the concept of catabolite repression

A

Phenomenon where the presence of glucose will inhibit beta galctosidase production, as bacteria preferentially metabolize glucose over lactose. In high glucose (and lactose) environments, the RNA polymerase is unable to bind to the DNA and therefore the lac genes are not transcribed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Explain what happens to the lac operon, in a high glucose environment

A
  • High gluose means low levels of cyclic AMP
  • low cyclic AMP means little/no CRP can bind to RNA polymerase.
  • Without CRP, RNA polymerase cannot bind to the DNA/promoter of lac operon
  • Therefore lac genes are not transcribed.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain what happens to the lac operon in a low glucose environment

A
  • Low glucose means high levels of cAMP
  • So cAMP can bind CRP
  • This means CRP can bind to the RNA polymerase/can be used by RNA polymerase to bind to the lac promoter
  • RNA polymerase binds and lac genes are transcribed., so beta galactosidase genes are produced, lactose can be metabolized now instead of glucose.
17
Q

Which source of energy is preferred by bacteria

A

glucose, always!

18
Q

What is CRP, what does it do and which molecule does it require

A

CRP = Catabolite repressor protein. Sometimes known as CAP, catabolite activator protein.

19
Q

What happens to the trp operon in the presence of Tryptophan

A

When tryptophan is present, it binds to the repressor molecule, and together they bind to the trp operator. This blocks RNA polymerase from transcribing the 5 trp genes.

20
Q

What happens to the trp operon in the absence of Tryptophan

A

When tryptophan is absent, the repressor molecule dimers are in their inactive form, and cannot bind to the DNA operator. Thus the operon is not blocked by repressor and the trp genes are transcribed, so tryptohphan is produced.

21
Q

How many structural genes are encoded by the trp operon

A

5

22
Q

Give an example of a repressible operon

A

The TRP operon. TRP acts as a co-repressor by binding to the trp repressor molecule

23
Q

What is IPTG

A

a synthetic inducer for the lac operon, but is not a substrate like lactose. IPTG can be used to induce Beta galactosidase production. (and not be broken down by it too) Used in synthetic biology experiments.

24
Q

Explain what an Operon is

A

A cluster of genes encoded for by a single promoter. Typically found in prokaryotes, very rare in humans and eukaryotes.

25
Q

Define cistron

A

this is an alternative word for a gene!!

26
Q

Explain what is meant by polycistronic messenger RNA

A

cistron = gene
poly = many
thus polycistronic mRNA means multi-genic mRNA. Where a single mRNA molecule carries multiple genes.!

27
Q

Explain what happens to the Lac operon in the presence of lactose

A
  • Allolactose binds to the repressor
  • Repressor dissociates from operator
  • Repressor molecule changes shape can no longer bind to the operator and block RNA Polymerase.
  • RNA polymerase can now transcribe the genes of the lac operon.
28
Q

Explain what happens to the Lac operon in the absence of lactose

A
  • Repressor molecule binds to the operator
  • This binding blocks the promoter region and blocks RNA polymerase transcribing
  • The genes of the lac operon cannot be transcribed in the absence of lactose
29
Q

Explain why the Lac operon can be described as an example of negative feedback mechanism,

A

Because, the lac genes are only transcribed when lactose is present in environment. As lac genes are made, they break down the lactose so that little-no lactose is left in the surrounding medium. Once no lactose left, the operon is repressed, as the repressor binds to the operator again .

30
Q

Which lac genes encodes the repressor molecule

A

The lac I gene

31
Q

Which gene encodes beta galactosidase

A

The lac Z gene

32
Q

What does the lac Y gene encode

A

permease

33
Q

What does the lac A gene encode

A

Acetylase

34
Q

In regards to the lac operon, which molecule is the substrate

A

Lactose

35
Q

Which molecule is the inducer in the lac operon

A

allolactose is the inducer as it binds to the repressor and allows transcription to take place.

Molecular Biology (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions