HYB: 201 -- Seedling Evaluation

This is a new scenario, although the =

topic has been covered before.  The
answers can be found in TWOI and =

GARDEN IRISES, but you don't need
either book to do the exercise.  =


This is much simpler than the recent
assignments involving quarterbreds,
but if you're not comfortable with the
concept of dominant and recessive
traits, you may want to search the
archives for those threads before
tackling this assignment.


Now, imagine the following:

You're working with tetraploid TBs.  You
have a seedling that's everything you want =

in a plant.  Strong grower, disease resistant,
etc.  But the flower is blue and you're =

working toward whites.  So we'll dub this =

breeder "OLD BLUE".

You've selected three good whites from your
seedling patch, but you're just getting =

started so you don't know anything about =

their genotypes.

WHITE ONE was your favorite -- clean &
clear with not a trace of blue. =


WHITE TWO was your second choice.  =

Nice flower with just a hint of blue in
the heart.

WHITE THREE had a hint of blue in
its bud, but otherwise you considered
it a nice flower.

You crossed the three whites not only
with each other but also with the blue, =

and have now bloomed the first =

generation of their seedlings.  =


Your cross of  OLD BLUE X WHITE ONE =

produced over a hundred seedlings and =

every one of them is blue.

Your cross of OLD BLUE X WHITE TWO =

gave you less than fifty seedlings -- but =

one of them is white.

Your cross of OLD BLUE X WHITE
THREE gave close to 75 seedlings --
roughly half of them white.

WHITE ONE X WHITE TWO gave almost
100 seedlings -- all blue.

WHITE ONE X WHITE THREE gave about
75 seedlings -- roughly half of them white.

WHITE TWO X WHITE THREE gave about
75 seedlings -- roughly half of them white.

This is not an exercise in statistical
analysis -- that's why I haven't provided =

specific numbers for you to crunch.
It IS a chance to test your logic and intuition.  =

Yes, of course I've made up the numbers --
and chosen them to lead you gently to the
correct conclusions.

QUESTION:
What genotypes would explain this =

breeding behavior?

HINTS:
1.  The scenario involves more than one =

      allelic series.

2.  Two of these hypothetical seedlings are
      homozygous for one series -- not
      necessarily the same one.

3.  Two are completely heterozygous for
      the series being studied.


If you already have the answers on the first
reading, you're obviously ready for "graduate =

school".

Beginners -- I expect you to puzzle over this =

one for a while.  =


Sharon McAllister
73372.1745@Compuserve.com
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