Re: HYB: color genes made easy (orig post 7/17/97)
Thanks so much for finding this for us, Linda. I've printed it out
and will study it along with other input. I wouldn't hold my breath
until I understand it, but I'm very grateful to have it. With each
study, I get a little closer.
Patricia Brooks, Iris Addict
--- In firstname.lastname@example.org, Linda Mann <lmann@i...> wrote:
> Turns out Tom Little's post wasn't about Punnett's square after
> sorry for the confusion. Took some serious searching even when I
> what I was looking for and I had to go to my printed copy to find
> figure it's worth posting again. Here is the original post:
> 1. GENES THAT DETERMINE IRIS COLOR
> Beware: I've made a few simplifications for the sake of
> only genes found in TBs are considered.
> 1a. Genes Affecting the Blue and Purple (Anthocyanidin) Pigments:
> V (dominant), allows the flower to produce purple pigments
> v (its recessive), no purple pigment produced
> I (dominant), inhibits the expression of purple pigments everywhere
> i (its recessive), lets the purple be expressed
> I-s (dominant), inhibits or reduces the expression of purple
> the standards
> i-s (its recessive), lets the purple be expressed everywhere
> PL (dominant), lets the purple be expressed everywhere
> pl (recessive to PL, dominant to pl-a), lets the purple be expressed
> along veins and petal edges (plicata)
> pl-lu (recessive to PL, dominant to pl-a), lets purple be expressed
> between veins, leaving clear veins, styles, and hafts (luminata)
> pl-a (recessive to PL, pl, and pl-lu) prevents the expression of
> 1b. Genes Affecting the Yellow and Pink (Carotenoid) Pigments:
> Y (dominant), allows the flower to produce yellow pigments
> y (its recessive), no yellow pigment produced
> [Note--the situation with yellow is more complicated than this.
> probably several genes involved; simple dominant/recessive model
> always work.]
> H (I just made this symbol up), causes the yellow pigment in the
> be distributed in a "halo". I don't know if this is dominant or not.
> breeders may want to chime in.
> A (I made this one up too), allows yellow pigment to be distributed
> throughout the flower
> a (its recessive), causes yellow pigment to be eliminated or
> T (dominant), keeps pigment in its yellow form
> t (its recessive), changes yellow pigment to pink
> 2. GUESSING YOUR IRISES' GENES
> Here are some rules to help you guess which of these genes a given
> have. You'll need to view this using a fixed-spaced font. An "x"
> least one copy of the gene is probably present, a "o" means none of
> genes can be present. (Since TB irises are tetraploids, there is a
> four of each type of gene.)
> [for these tables, to get them to line up right, try using courier
> other fonts - lm]
> V I I-s Y A H T PL
> 2a. Selfs:
> blue or violet x o o o x
> red, brown, or black x o o x x o x x
> yellow x x x o x
> pink or orange x x x o o
> white x o
> 2b. Bicolors:
> purple or blue amoena x o x o x
> yellow amoena x x o x
> pink or orange amoena x x o o
> variegata x o x x x x x
> 2c. Plicatas
> blue or violet on white ground x o o o
> red or brown on yellow ground x o o x x x
> violet on pink/orange ground x o o x x o
> no plicata markings on standards (various ground colors)--same
> but at least one I-s
> luminata (various ground) x o o o o
> 2d. Halos
> yellow stadards, falls white w/yellow halo (e.g., Debby Rairdon)
> x x x x
> pink standards, falls white w/pink halo (e.g., Queen of Hearts)
> x x x o
> brown standards, falls violet w/brown halo (e.g., Brown Lasso)
> x o o x x x
> If you study the chart for awhile, you'll find you get the "feel"
> and can guess the genes of color combinations not on the chart. For
> example, 'Broadway' has clear yellow standards, and white falls with
> red-brown plicata markings. It must have V (because the plicata
> are made with the purple pigments, not the yellow ones), it cannot
> it must have I-s (because there are no purple markings in the
> it must have Y, it must have H (because the center of the falls are
> but there must be some yellow around the halo to account for the
> the plicata marks), it must have T (because the yellow is yellow,
> pink), and cannot have PL or pl-lu.
> 3. WHEN YOU CROSS 'EM
> As you can see from the chart above, in most cases we only know
> particular dominant gene is present (at least one) or absent
> usually don't know exactly how many copies of a dominant gene may be
> But if we're just making an "educated guess" of what might come out
> seedling patch, that's good enough. Here are the rules:
> 3a. If neither parent has a particular dominant gene, NONE of the
> will have it. Thus crossing two plicatas can never produce a violet
> because neither parent has the PL gene needed to make this happen.
> 3b. If only one parent has a particular dominant gene, AT LEAST
> seedlings can be expected to have it too, on average. (If more than
> copy of the gene is present, it may appear in most or all of the
> 3c. If both parents have a particular dominant gene, AT LEAST 3/4
> seedlings can be expected to have it too, on average.
> Using these rules, you can make a good guess which of the dominant
> the seedlings may end up with, and predict their color patterns.
> 4. GETTING FANCY
> If this is not enough fun, and you want to get a better idea of how
> genes of each type the parents may carry, you need to do pedigree
> If an iris comes from crossing a violet self and a plicata, for
> know it can have at most two PL genes out of its total of four; the
> two (which came from the plicata parent) are almost certainly pl. In
> way, you can sometimes narrow down the possibilities of what
> genes may be present, and in what dosage.
> Ultimately, of course, if one knows the full genotype of the
> can calculate in detail the percentages of seedlings having each
> genotype. Genetics books have instructions and exercises for this
> thing. In practice, though, we hardly ever know the complete
> the parents, and we rarely care about the exact percentages that
> appear in the seedling bed (the exception being with controlled
> designed to study how a particular trait is inherited).
> These "rules of thumb" are a _lot_ easier to use than the
> are explained in the textbooks, and in most cases give a very good
> what to expect from a cross.
> Happy irising, Tom [Tadfor Little]
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