What is SPI phenotype?

Abstract. The old gene product of the P2 prophage interferes with plaque formation by lambda wild type phage but allows lambda phages whose red and gam genes have been deleted to form small, visible plaques (the lambda Spi- phenotype). The old gene product also kills Escherichia coli recB or recC mutants.

What are lambda insertion and replacement vectors?

The key difference between insertion and replacement vectors is that the insertion vector has the ability to insert moderate lengths of foreign DNA while replacement vector has the ability to accommodate larger lengths of foreign DNA.

What is Vitro Packaging?

In vitro packaging involves the use of two bacterial extracts: one from cells infected with a D mutant phage, and a second from cells infected with a phage mutant in gene E. Mixing these two extracts allows in vitro complementation and results in the ability to assemble mature phage particles.

What are lambda vectors?

Bacteriophage lambda has been in use as a cloning vector for over 25 years, and has been used extensively as an expression vector. The efficiency of packaging and infection, and the simplicity of plaque screening are advantages of lambda as a cloning vector.

What are stuffer fragments?

Stuffer-fragment meaning (genetics) A section of DNA contained within the genome of lambda vector that is replaced by the DNA to be cloned. noun. 1.

What is SPI selection?

The selection system used to selectively replicate recombinant phage involves yet another observation made by phage geneticists. Thus, wild-type phage are Sensitive to Ps Interference (spi). Phage genes responsible for the spi phenotype are carried on the stuffer fragment of the insertion vector.

What is lambda phage vector?

Enterobacteria phage λ (lambda phage, coliphage λ) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli. However, under certain conditions, the phage DNA may integrate itself into the host cell chromosome in the lysogenic pathway.

How did Hershey and Chase proved that DNA is the genetic material?

Complete answer: Two scientists Alfred Hershey and Martha Chase proved that DNA is a genetic material by working on bacteriophages. After doing this, they observed that the viruses which were grown in radioactive phosphorus contained radioactive DNA. There was no presence of radioactive protein.

How is in vitro packaging of lambda based vectors is done?

In the normal growth cycle of bacteriophage lambda, the proteins that ultimately form the head of the phage particle are assembled into an empty precursor of the head (prehead); the phage DNA is replicated separately and then inserted into the empty head particles-a process known as packaging.

Which protein recognize the cos site of lambda DNA?

The 12 nucleotide 5′ overhangs at the cos-ends of the linear Lambda DNA are the result of a cut by the enzyme terminase. This enzyme is encoded by Lambda itself and acts like a restriction enzyme during the replication of the phage DNA. It is an endonuclease specific for the cos-site in multimeric phage DNA.