Overview of Lambda Phage genome

Hello Friends

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The topic I am going to brief about is Lambda Phage lysogenic and lytic phase gene regulation introduction.

It is a Bacteriophage which is consist of a capsid, a tail and tail fiber.

It has double stranded, linear DNA as genetic material, 50Kb genome with 50 genes.

The linear genome has 12bp cohesive ends which are complementary and it gets circularize as soon as it infects the bacterium.

Now, gene regulation of lytic and lysogenic phase takes place with the help of regulatory proteins.

A region of genome of Lambda has sequence like this

                                                                                                   

PL

cI

PRM

PR

cro

 All other genes are outside this region except one and are transcribed directly from P_L and P_R or from other promoters whose activities are controlled by their products.

P_RM transcribes only cI . It is repressor maintenance promoter. It is weak promoter and efficient only when activator bind just upstream.

P_L and P_R are strong promoters and do not require activator.






 P_{L and} P_RM  codes towards left and P_{R codes towards right.}

For lytic phase  P_L and P_R are switched on and P_RM  is switched off and for lysogenic phase P_RM and rest two are off.

cI encodes Lambda repressor which can act as both repressor and activator.

As a repressor it s target is σ subunit of RNA Ploymerase , the adjacent to the part of σ which recognize -35 region on DNA.

As activator it works like CAP as in Lac operon.

The cI and cro are functional in dimeric form.

Rest I will discuss in next blog.

          

Hope this will help you all. See you all in next blog.

Thankyou for reading.