[Drosophila] Mutation not as described

Keith Maggert kmaggert at tamu.edu
Mon Jul 25 13:11:44 EST 2005


It seems to me that perhaps two things have happened:

1 - The stock (prior to or while at Bloomington) became contaminated  
with a X chromosome that did not contain the mutation.   
Alternatively, the coverage of FM6 does not include the location of  
your mutation.  The latter explanation may be possible, since FM6 has  
the same problem as FM4: funny double-crossover genetics (see the  
Redbook).  Either way, this would explain why you were able to obtain  
homozygotes and hemizygotes that did not express the phenotype.

2 - After you recovered the mutation, you probably also got another  
mutation on the same chromosome (either from a contaminating  
chromosome or as a spontaneous mutation).  This second mutation may  
confer the subviable/subfertile phenotype.

Now that you have your mutant, but the rest of the chromosome is  
suspect, you should "clean it up."  Cross females mut/FM6 to yw/Y  
males and collect mut/yw virgins.  Backcross a few generations to yw/ 
Y males to get rid of secondary mutations by recombination.  Each  
generation, set up a few dozen vials with individual females, and  
always monitor the presence of the mutation by its expression in  
sibling males.  After a few generations, unless the second mutation  
is closely linked, you should be able to cross females to FM/Y for  
two generations to rebalance it.  I'd recommend a different  
chromosome 1 balance.  FM7 is always in season.

Hope this helps,

Keith Maggert

Keith A. Maggert, Ph.D.                           Assistant Professor
Texas A&M University                            office (979) 845-6610
Department of Biology                              fax (979) 845-2891
College Station, TX 77843-3258, U.S.A.              kmaggert at tamu.edu

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