Hi there, thanks very much for your links and your chart! I've finally plucked up the courage to start working on Roses, and working towards a
Blue Rose.
I think there's a slight issue with your interpretation of
Orange and
Purple roses. You're right that there is a 25% chance of getting the kind of
Red rose that can give a
Blue offspring; however, there is also a 25% chance of getting a
different kind of
Red rose that
cannot give a
blue offspring just with other
reds. This might be really frustrating, because your "
Hybrid red" roses could be a complete wild goose chase if you're not careful, particularly if the expectation is that you might have to wait months at a time for a
blue rose even if it *is* the right type!
The upshot of this point though is it also suggests a much simpler way to reach
Blue roses than going around the house of colours - the "wrong" type of
Red rose can be used in an extra step to make the "right" type of
Red rose; in fact, we can very easily make the "wrong" type of
Red roses to start a production line!
Let's step through why this is the case:
First, what is a
Blue Rose? A Blue rose has the genotype:
RRYYwwss, according to the spreadsheet. This means it has to have both dominant R and Y genes. And all
blue roses have this genotype.
Next, a
Purple Rose is all recessive genes - the most common variety (which we get from two white parents) has the genotype
rryywwss (other genotypes expressing as purple exist but don't really help us out much).
Lastly,
Orange Roses can be found a couple of ways, but both of them result in a plant with the genotype
RrYyWWss (again others exist but this is the one we use here).
Orange roses carry both dominant and recessive genes in R and Y, but has both dominant W genes.
The reason we breed
Orange and
Purple roses together to get
Blue roses is we want to do two things - we want to breed in w recessive genes, while keeping the dominant R and Y genes. When we breed an
Orange and a
Purple together, we definitely breed in the recessive gene; the random factor is whether we get to keep the dominant R and Y genes. It is an equally likely coin toss whether the new flower will or will not inherit either of the two dominant genes.
So there are four possible outcomes and each one has a one-in-four chance of happening. The one we really want is this one:
RrYyWwss - this has a red flower, but also has dominant Y and recessive w genes - let's call it
Red-Y. Breeding these together to get a blue rose might take a while but it will get there eventually.
The other three are no good to us, because they lack either the dominant R or the dominant Y that we want. Fortunately, we can easily rule out either of the two types that haven't got the dominant R gene, because their flowers will be
Yellow.
However, we can't say the same if we're missing the dominant Y, because that flower is
RryyWwss. This is a
Red rose too (let's call it
Red-W), but because it lacks the dominant Y gene, it's no good for making
blue offspring without further intervention.
What this means is that even if you do get a
Red rose from breeding an
Orange and a
Purple together, there is only a 50-50 chance that your rose is a
Red-Y; you might instead get the alternative
Red-W which isn't even
capable of producing
blue babies.
So what's the fix? I have three suggestions to help reduce the risk of wasting a long time on
Red-W roses, all of which might be useful, particularly if done together!
1) Test the
hybrid red roses before you start them breeding. Our worry is that we might be introducing a rose into the pool that doesn't have the Y dominant gene, so we'd like some sort of way to test our roses and find out whether they have that gene or not.
You can do such a test by breeding our
hybrid red rose with a
Black rose! If we breed a black rose (genotype RRyyWWss) with:
- a Red-Y, then there are three possible colours the children might have - Red, Black and Orange.
- a Red-W, then there are only two possible colours the children might have - Red and Black
So if we start by breeding the hybrid red with a black rose, and it has an orange child, then you know it's a Red-Y and is suitable for making Blues with others of its genotype.
2) When we've separated them out, we can use
Red-Ws to breed
Red-Ys - just cross them with
seed Yellows! All
Reds that we get from this will be
Red-Ys (though not every child will be red)
Once you know this, though, there's an obvious point to ask which is "Why not just breed
Red-Ws in the first place and use these to breed
Red-Ys?" And in fact this is easy to do - you can breed a
Purple and a Black rose to get a guaranteed
Red-W.
You can also just breed seed White roses with seed Reds for a one-in-two chance to
get either Red-Ws or Pink roses.
3) If you do want to follow the above method though, you can also fix the odds of getting a
Red-Y a bit in your favour by allowing your
Orange roses to breed together, and using a
"Second Generation" Orange rose when pairing with the
Purple rose.
Our basic
Orange roses have quite an unstable genotype - they have recessive r and y genes, as well as their dominant R and Y counterparts. The reason we sometimes get
Red-W plants is that we can lose the dominant Y when crossing. If we can breed an
Orange Rose that has *both* dominant YY genes then we'd never get
Red-W children.
All
Orange roses we get from crossing parents created using the above methods do have at least one dominant R and Y (if the child has both recessive yy then it is either black, red or white, and recessive rr is white or yellow). What this means is we can't do worse by using an
orange variety found from crossing other
orange roses. Not every child of two
orange parent roses is itself
orange, but those that are have a one-in-three chance of having both dominant YY genes; that's no guarantee, but it does reduce the odds of leading us down a genetic dead end.
(
Oranges found during testing other
Red-Ys can help too - they're never going to be dominant YY, but they might be dominant RR which reduces the possibility of
Yellows.)
I don't know if this makes any difference to anyone, but it seems worth highlighting an additional step or two that people might want to take in pursuit of the mythical
Blue Roses!
