Genetics Problem

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Genetics Problem

Post by aloyng » Tue Oct 03, 2006 8:59 am

How do you do the following question. What are the possible explanations? Need HELP! :(

In drosophila a temperature sensitive mutation in the SNAP-25 gene causes larval paralysis and death if the larvae are subjected to high temperature. This mutant phenotype is recessive (requires that the temperature-sensitive mutation is present in both copies of the gene before the larvae paralyse at high temperature). In contrast, larvae that contain a knock out of the SNAP-25 gene are homozygous viable (when both copies of the gene are knocked out the larvae are normal). Explain the role of the SNAP-25 protein in neuronal cell signalling and in doing so give an explanation for the paradoxcial behaviour of the two SNAP-25 mutants.

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Post by LilKim » Tue Oct 03, 2006 4:56 pm

From reading your question I would guess that this has to do with folding problem. From my vague memory of SNAP and SNARE these things are protiens necessary for vessicle fusion and targeting there are a WHOLE family of tham and ... I would guess that the SNAP-25 protien is not an essential gene (because a knock-out is vible).. maybe this would be due to an upregulation of other SNAP which would provide a rescue effect.

however the the temp. sensitive mutatnt is .. heated the protein may conform to a abnormal shape that is disrupting neuronal signaling and somehow just "gumming-up the works" and killing the larvaie (something like a dominant negative, but maybe not exactly)

... however a fly in the heterozygous state has enough of wt protein (and/or other protiens from the SNAP family) to compensate for the protein that isnt' working properly... and this would result in 'viable' larve

Anyways, this is just a guess I really don't know what's truely going on ..nor do i know the exact context of the question in reference to what you've learned in class.

BUT ... i think that you should look at it from a PROTEIN FOLDING stanpoint

Hope this helps

Buena suerte!

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