HYB: Chuck's hose/pigment analogy

Thought while I was at it, I would cross post this one with a different
subject line as well:

<  Some information here to help us with an analysis. The distribution
of
                   factors such as intensity of yellow or can be viewed
as continuous or
                   discreet. Discrete can be in steps. Look at the
heights of bearded iris, all
                   types from pumila to the tall TBs at 40"+. This forms
a continuum and
                   plotting on a graph with height being the horizontal
axis and the number at
                   each height being the vertical axis , we would end up
with a curve.

                   Most factors in nature have what is called a normal
distribution of variance.
                   That is all the various small factors making up an
item cause a variation.
                   The more factors the narrower the curve, the more
factors the wider the
                   curve.

                   We know that we have several different
classifications of height/type
                   classifications of bearded iris EG: MDB, SDB, IB, BB,
TB etc. If this was
                   only a discrete difference then all MDB would be 6",
all SDB 12" etc. This is
                   obviously not the case. The plot of height versus
distribution would give us
                   several peaks. One for each median (average) height
for that class. Thatr is
                   there would be a peak for MDB, for SDB IB, TB and
minor peaks for MTB and BB
                   (not as many varieties and numbers count). Thus we
are dealing with both
                   discrete and continuous. Genetically MDB, SDB, IB and
TB are different. They
                   all have different sets of genes. The Iris pumila has
four sets of 8 genes
                   8/8/8/8 and in crosses with TB 12/12/12/12 have
produced MDB 8/8/8/12, SDB
                   8/8/12/12, IB 8/12/12/12. each one of these types
could produce their own
                   normal distribution curves ( I'm ignoring judging and
registration rules here
                   and focusing on genetic classification) that are very
smooth without any sub
                   peaks or any skewing (more on one side of the
median(average) then the
                   other). Thus if we didn't know the genetics (or have
the parentage) we would
                   have to classify an unknown into a category based on
its height ( for the
                   moment I'm ignoring the other information I might
have). Thus an iris 16"in
                   height would be classified into SDB even if it is IB
genetically, just on the
                   lower end of its scale. An SDB that is 7" tall would
be classified as an MDB
                   even if it is genetically an SDB. If we had the
parentage we would be able to
                   more accurately assess what it is genetically.

                   The same principals apply to dissecting a cross with
as much variance as this
                   one. When it comes to analysing the category we place
something in both
                   factors have to be considered. FoF  would seem to be
tttt, but is more
                   apricot-yellow then pink. We use this knowledge to
place seedling #4 into
                   tttt  category , although other interpretations are
possible.

                   The same with looking at the amount of yellow and
amount of blue in each
                   seedling.
                   The removal of anthocyanin is referred to either
Dominant reduction of
                   anthocyanin ( not referred to a complete removal of
anthocyanin) referred to
                   as "I", or recessive removal of anthocyanin .  To
tell which, (dominant or
                   recessive) look at parents and look at the seedlings,
trying to ignore other
                   factors, and keep in mind what else may mask the
factor we are looking at.

                   The yellow is more complicated as Robin noted.  I
have some evidence that the
                   cream (flavanoid pigments) and beta-carotene and
alpha-carotene may act
                   independently and may be what is referred to as y1,
y2, y3.

                   With anthocyanin there is about 20 steps in
production of anthocyanin from
                   its colourless precursors into the visible form. This
is like a garden hose
                   with 20 shut off valves in it. If any one is turned
off, the water
                   (anthocyanin) doesn't come out the other end. In
various plants about 8 of
                   these steps have been blocked. In iris there are
several, more then 3 and
                   less then 6, that can turn off production.

                   With the yellows, the cream flavanoid seems to be
completely independent from
                   the other yellows, no shared precursor, a different
chemical chain.

                   With the carotenoids it is like we have one garden
hose coming from the tap
                   with  a "Y" junction at some point ( chemical
biosynthesis info, not just
                   observation). Now put at least one tap in each line.
Thus you can cut off the
                   main tap, no beta or alpha carotene. You can turn one
of the "Y" branch taps
                   and remove either apha or beta-carotene or you can
turn both off at the y
                   branches to remove both, the same as turning off the
main tap.

                   I hope this helps but I'm afraid it may confuse
everyone.  I don't have any
                   pictures of normal distributions curves handy to post
, other wise I would.

                   Chuck Chapman>


--
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.korrnet.org/etis>
American Iris Society web site <http://www.irises.org>
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