RE: [SpaceAgeRobin] RE: Space Age Genetics

With a partial dominant, it would need 3 or 4 dosages of SA to produce an appendage. The shelf may be either one ote two SA genes. Thus the showing up of 3 or 4 dosages necessary to show appendage would not occur as readily as may be assumed. Also since there is some propensity for SA gene to produce some flower distortion the two dosage plants would tend to be discarded.
Thornbird with this sort of history would likely be 4 dosage SA gene.
A test of this would now involve crossing TB X the plants that seem to "Inhibit" SA or could be 0 dosages of SA. If the partial dominance theory is correct then this cross should produce almost no SA as would the inhibition theory but F2 would sort out in a punnett square analysis. I havn't yet checked if F2 would distinguish one idea from the other.

There are a lot of similarities to the PBF trait. Some growing conditions produce effect, doesn't show up in others in same plant. This is typical of partial dominace and also to multiple allele factors. 

Don't dismisss this theory too soon. It's still a viable possibility and the results are not in yet.

Chuck Chapman

"Neil A Mogensen" <neilm@charter.net> wrote:

>Chuck, looking at the family tree for THORNBIRD on the HIPS "Quick Fix" page (or on the Dykes Medal page), doesn't suggest a partial dominant.  Generation after generation of outcrosses to non-SA co-parents produce SA's.
>
>If those co-parents carried any of the required make-up for an SA, there would surely have been more "breaks" in seedlings than seem to have occurred.  The only ones I know of are incidents in the Sass seedlings (which is no surprising, since Sass bloodlines are involved in all of the known "breaks").
>
>Two other incidents occur in California, one for Mrs. Lohman, the other for Tom Craig.  Other than the appearance of UNICORN in Lloyd Austin's inbreeding seedlings and varieties (ADVANCE GUARD) which display what we are calling "BSE" for beard spine extension.
>
>I have seen conspicuous BSEs on a number of irises, especially those from inbred plicata lines (thus strong to Sass ancestry).
>
>I think that you are quite right in suggesting that the appearance of SA's is not a single gene, but a combination of at least two.
>
>What makes this so complex is that the SA trait is generated right at the beginning of blossom part differentiation in the embryonic bud.  Growth hormones, enzymes that mediate differentiation of falls from the growing tip are undoubtedly involved, and it may be that the SA traits arise from a modification or genetic change in one or more of those.
>
>This is an onion that will not quickly be peeled.
>
>Neil Mogensen  z 7  western NC mountains
>

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