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Prep4USMLE Forum » USMLE Step 1 Forum » Microbiology Forum

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6 Posts

Palaniappan
Forum Senior

Topics: 30
Posts: 148

01/15/07 - 01:04 PM

Virus A can't infect human cells.After exposure to virus B in non-human cells,Virus A acquirs the ability to infect epithelial cells .However,viral progeny of Virus A still cannot infect human cells.What is the most likely phenomenon occured?

A.Reassortment
B.Recombination
C.Transformation
D.Phenotypic mixing
E.interference

Please explain your answer
Thanx smiling face

Ancylostoma
Forum Guru

Topics: 42
Posts: 642

01/15/07 - 01:07 PM

D Phenotypic mixing Virus a when first mixed with virus B basically trades outer coating (word is escaping me for the moment,) These new proteins allow it to infect the human cells. however, virus a still has its original Dna, so the progeny made are like the original prior to mixing, unable to penetrate human cells .

Palaniappan
Forum Senior

Topics: 30
Posts: 148

01/15/07 - 01:36 PM

Yes..It is D..I was wondering whether transformation can cause viral progeny,after transformation can infect the cells or tranformation can just alter the genetic composition of the host cell?

Palaniappan
Forum Senior

Topics: 30
Posts: 148

01/15/07 - 01:37 PM

Palaniappan wrote:
Yes..It is D..I was wondering whether transformation can cause viral progeny,(after transformation )can infect the cells or tranformation can just alter the genetic composition of the host cell?

Ancylostoma
Forum Guru

Topics: 42
Posts: 642

01/15/07 - 06:34 PM

transformation is the uptake of the naked pieces of dna and this is usually involving bacteria. I have never heard of a virus being able to do so. Even if it could pick up this new DNA, it wouldnt be able to change its protein coat /capsid which is mainly responsible for it entry in the cell. Remember virus requires cell machinery to do anything. Besides that point, you must know that penotype mixing means that the two viruses switch coats, thus there target cells may changre for that generation. The dna never changes and thus the progeny turn out to be normal.

Palaniappan
Forum Senior

Topics: 30
Posts: 148

01/15/07 - 07:02 PM

Thanx anky..

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