HYB: genetics

From: Sharon McAllister <73372.1745@compuserve.com>

Jeff Walters wrote:

>  IMMORTALITY
>  has no recent ancestors that are pink, and probably does not carry the
pink
>  genes at all. Therefore, even if it is crossed with a pink iris it is
>  unlikely that any of the offspring (seedlings) will be pink. 

Quite true.  But those of us who work with recessives are accustomed to
assessing the POSSIBILITIES as well as the PROBABILITIES, and the pattern
of pinks in IMMORTALITY's family tree [see the Ahnentafel I posted
previously] is such that it could carry from 0 to 4 doses of the t-factor. 
Recent ancestors can certainly be carriers for pink without expressing it.

From IMMORTALITY's appearance, we know that regardless of how many doses it
carries, it must also have the carotenoid inhibitor -- but its child, SUNNY
DISPOSITION, tells us that it carries only one or two doses of the
inhibitor.  This means that IF it carries at least two doses of the
t-factor, pinks could show up in the first generation of an an outcross to
pink.  Hence Lloyd's original question....

If it carried four doses of the t-factor,  we'd expect about half pinks if
it were crossed to pink -- and so far we have no reports to that affect.

If it carried three doses, we'd still expect a significant number of pinks.

Turning this around, if ANY offspring of a cross to pink came out pink that
would be confirmation that IMMORTALITY has  two or more doses of the
t-factor.

If it has only one?  It wouldn't show up in the first generation, but would
increase the chances of getting pink in the second generation.

So this takes us back to the Ahnentafel.....    Has anyone crossed any of
the ancestors2 through 7 with pink TBs?  If so, were there any pinks among
the offspring?

Sharon McAllister
73372.1745@COMPUSERVE.COM


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