Question

A) Mutations present within a single gene can be rescued if they are located in a certain distance from each other” discuss. What would be the rescue scenario if the mutations overlap? B) Explain how a retrovirus, which has an RNA genome, is able to integrate its genetic material into that of a host having a DNA genome.

Answer 1

Dear student, due to constarint of time we are asked to answer only one question ... Plz separately post thw question unaswered...

i m amswering question B here... Thanku ...

B). A retrovirus is an RNA virus that is duplicated in a host cell using the reverse transcriptase enzyme to produce DNA from its RNA genome. The DNA is then incorporated into the host’s genome by an integrase enzyme...

The virus itself stores its nucleic acid in the form of an mRNA genome and serves as a means of delivering that genome into cells it targets as an obligate parasite (a parasite that cannot live without its host). That process of delivering the genome into cells constitutes the infection. Once in the host’s cell, the RNA strands undergo reverse transcription in the cytoplasm and are integrated into the host’s genome, at which point the retroviral DNA is referred to as a provirus......

So, the information contained in a retroviral gene is used to generate the corresponding protein via the sequence: RNA → DNA → RNA → protein.... Eg is HIV causing AIDS....

DNA integration is a unique enzymatic process shared by all retroviruses . During integration, double-stranded linear viral DNA is inserted into the host genome in a process catalyzed by the virus-encoded integrase (IN). The mechanism involves a series of nucleophillic attacks, the first of which removes the terminal 2 bases from the 3′ ends of the long terminal repeats and of the second which inserts the viral DNA into the host genome. IN specifically recognizes the DNA sequences at the termini of the viral DNA, juxtaposing both ends in an enzyme complex that inserts the viral DNA into a single site in a concerted manner. Small duplications of the host DNA, characteristic of the viral IN, are found at the sites of insertion. At least two host proteins, HMG-I(Y) and BAF, have been shown to increase the efficiency of the integration reaction.