Sordaria, crossing over

Marty Sachs msachs at
Sun Dec 5 16:30:47 EST 1993

In article <93333.202638WRATHAL at> <WRATHAL at>
>In article <1993Nov23.223337.856 at TYRELL.NET>, bengel at TYRELL.NET (Jason Bengel)
>> Using Sordaria fimicola (a species of ascomycete), I would like to
>> determine how often crossing over occurs between a wild type of Sordaria
>> and a mutant tan type of Sordaria.
>Sachs is correct - the answer is you can't. Assume that the mutation is a
>substitution, then both the wildtype and mutant occur at the same
>nucleotide - can't separtate the same thing  ( :(  - even PCR is not
>capable of this wonder.
>>  Does anyone know if this would work
>The only way to make it work is to cross two tan strains - any black spores
>would indicate a recombination event. You wouldn't even need ordered tetrads
>to do this. Note that this is recombination between alleles in the classical
>sense. I am sure that this has been done, but you would have to go back to
>the literature of the 60's to find it.

This is correct, but only if 1) the two tan strains are known to have allelic
mutations caused by independent events and are not overlapping and 2) the
occurrence of "recombinant" black spores is more frequent than the "revertant
rate" to black spores in either parent.

 -Marty Sachs
USDA/ARS & Agronomy/UIUC    msachs at [internet]
S108 Turner Hall            msachs at UIUCVMD [bitnet] 
1102 S. Goodwin Ave.        (217) 244-0864 [phone]
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