100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Previously searched by you
Previously searched by you
logo
Lambda Phage Gene Regulation (MCB3026F) notes CA$4.09   Add to cart
Quickly navigate to
Preview
  2.  
  3. University Of Cape Town (UCT)
  4.  
  5. Molecular Genetics and Genomics (MCB3026F)

Class notes

Lambda Phage Gene Regulation (MCB3026F) notes

2 reviews
 10 views  2 purchases
  • Course
  • Molecular Genetics and Genomics (MCB3026F)
  • Institution
  • University Of Cape Town (UCT)

Comprehensive lecture notes for the Lambda Phage Gene Regulation module covered in MCB3026F. These notes cover all content taught in lectures as well as additional materials (powerpoints, textbooks) required to succeed. These notes were created by a student who achieved a distinction in this course.

Preview 2 out of 13  pages

Document information

  • February 8, 2024
  • 13
  • 2022/2023
  • Class notes
  • Assoc prof suhail rafudeen
  • All classes

Subjects

  • genetics

Written for

  • University of Cape Town (UCT)
  • Molecular Genetics and Genomics (MCB3026F)
All documents for this subject (6)

2  reviews

review-writer-avatar

By: enyasteyn • 4 months ago

review-writer-avatar

By: zanelelavelle • 6 months ago

Seller

avatar-seller
ggauntlett

Reviews received

Content preview

MBC3026F

Lambda phage gene regulation

Lecture 1
Transcription
- transcription is the synthesis of RNA from a DNA template, transcription of DNA into RNA is done by RNA polymerase
- RNA polymerase makes RNA starting at the DNA promoter regions
- mRNA transcript stability is called the mRNA half-life and is dependent on mRNA structure and ribonuclease activity

Translation
- in translation, an mRNA template is used for the ribosomal synthesis of a protein from amino acids in sequence
- the translation initiation region (TIR) indicates the first correct codon for the ribosome and consists of the shine Dalgarno
and initiation codon
- shine Dalgarno is upstream of the initiation codon and allows proper aligning of the mRNA on the ribosome and this
sequence determines the efficiency of translation
- the initiation codon codes for the first definable amino acid
- the stop codon terminated translation
- similar to bacteria and viruses, have polycistronic mRNA which means can have a number of genes transcribed from the
same piece of RNA

Life cycle:
Lytic (reproductive) cycle
1. Adsorption and penetration: Phage attaches to specific receptor and injects ds DNA (in the environment, the phage finds
an appropriate host and absorption has a very specific host range as the phage only recognizes a specific type of bacterial
species due to the presence of a specific receptor)
2. Phage forces bacteria to make viral DNA and proteins
3. Phages assembled where virus DNA is packaged within virus protein coat (this is often self-assembly)
4. Mature virus released by cell lysis
5. Phages that reproduce using a lyric cycle are virulent phages (virulent/lytic phages cannot establish lysogeny)

Lytic cycle
- Phage recognizes receptor on host cell and injects its DNA, forcing the host to make many copies of its DNA, it matures,
makes phages which get released by the cell; Lytic cycles can last from as little as 2 minutes
- lambda phage is a lysogenic phage, and its lifecycle is usually about an hour
- its DNA will enter the host cell; host will start to transcribe the DNA while it simultaneously degrades the host DNA, so
cell machinery is focused on making copies of viral DNA and phage components, phage DNA gets encapsulated in the
phage heads; some host DNA may be incorporated into a phage head, and this is called transduction, cell host lyses and the
phages are released




Lysogenic cycle
- not all viruses can do this, only certain viruses
1. Adsorption and penetration: Most viruses have a very narrow host range, hence have specific recognition and adsorption
to host bacteria
2. Phage does not take control over the bacterium: virus genome integrates into the host genome (a prophage is a virus that
has integrated into the genome of a bacterium)
3. Phage DNA reproduced along with the bacterial chromosome for long periods and appear normal phenotypically but are
normally more pathogenic than bacteria (a bacterium with an integrated phage is known as a lysogen)
4. Lysogens can produce phage particles under stressful conditions such as DNA damage conditions
5. Phages that can establish lytic and lysogeny are called temperate phages which is a phage that can establish lysogeny

, - under stressful conditions, the phage will exit the lysogenic cycle and enter the lytic cycle

Lifecycle of a Temperate Phage Structure of Bacteriophage Lambda
- has a head, collar, tail and tail fiber
- the head contains the double stranded
linear genome




Lambda phage (λ)entry
1. Adsorption: phage identifies host E. Coli. The J protein in the tail tip of the phage binds to the E. coli outer membrane
protein (LamB)
2. Phage DNA injection: linear phage genome is ejected into the cell via an E. coli sugar transport protein, PstM, located in
the inner membrane
3. DNA circularization and ligation: once the DNA has been injected into the cytoplasm, it has cohesive/sticky ends
where the left end and right end (cos sites) come together and form a circle i.e., phage DNA circularizes using cos sites (12
bp GC rich cohesive ends) and host DNA ligase seals nicks which prevents degradation by exonucleases
4. Supercoiling: Host DNA gyrase supercoils lambda DNA, AT rich regions unwind and drives initial transcription and
initial replication (as the supercoiling allows host polymerases to access the DNA promoter region), note that this
circularization also protects the phage DNA from being digested by host DNases which recognize and attach the cos sites
5. Theta replication: phage replicates initially via Theta replication producing copies of the phage transcription and
translation of certain phage genes




Genome of lambda phage
- has a very ordered genome
- for the lytic cycle, need lysis proteins, tail proteins, head proteins and these genes are all clustered together and these genes
are often on polycistronic mRNA therefore get translated in an ordered process, one by one
- the lysogenic cycle involves integrating into the bacterial genome or getting out of the genome so requires integrase and
excisionase genes as well as recombination proteins which are also clustered together
- the regulatory proteins are clustered together
- has a large number of operators and promoters as well as termination sites

Genome regions of lambda phage
- the head/tail: codes for structural proteins
and terminase protein
- recombination: required for integration and excision, codes for Int and Xis
- regulation: two regions; one of which codes for proteins that control the switch between lysis and lysogeny and the second
region codes for Q protein and anti-Q mRNA; these regions also have key promoters and operators
- DNA replication: code for O and P proteins and contain an origin of replication
- lysis: codes for proteins responsible for lysis
Functional clustering

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller ggauntlett. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for CA$4.09. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

83637 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling
CA$4.09  2x  sold
  • (2)
  Add to cart