Expert: Florence M Rollwagen - 4/15/2009

Question
I have a question in regards to vaccines and mutants.  First off, what is a "deletion mutant"?  It mentions it in my text but it doesn't explain the difference between a deletion mutant and a general mutant (are they the same?).  
Second, there is an interesting question at the end of the chapter that I'm trying to understand-  It states that "In the process of creating a vaccine for the ebola virus, researchers have created a strain of virus that is a deletion mutant for an essential gene.  How can they grow this virus so they have sufficient amounts to work with?"

If you are able to assist me with this topic, please guide me to an individual who might. Thank you!  

Answer
Hi again, Jasmine:

A deletion mutant is when a part of the genome is lost.   It can happen in any organism, including viruses.

When we talk about mutations, we can discuss DNA mutations (a change in the DNA sequence) such as point mutations, insertions, deletions (leading to frameshift mutations), or silent mutations.

We also talk about changes in chromosome structure, where entire parts of the chromosome are affected, potentially including many genes.  These can (also, and confusingly) be called deletions, insertions, translocations and duplications.

Not sure which one you mean, so I gave you both.

When we create a vaccine, sometimes we use an attenuated (weakened) live virus, such as the shingles vaccine.  One of the vaccine candidates for Ebola is also an attentuated virus in which part of the virus genome has been deleted.  For example the GP-125 mutation has 125 nucleic acids of its glycoprotein (gp) sequence deleted.

Virus vaccine candidates can be grown in tissue culture (in susceptible cells) for analysis and propagation for vaccination.  http://en.wikipedia.org/wiki/Cell_culture  (scroll down to viruses)


Hope this helps, please write back if you have more questions.