I'm assuming you know how to use a punnet square and what not, now what you can do would be to breed two guppies together, say a turquoise and a leopard.
If the traits blend turquoise and leopard are incompletely dominant to each other. If it shows equal amounts of turquoise and leopard, they are codominant to each other. If the traits show turquoise then turquoise is dominant over leopard. And if leopard is shown, turquoise is dominant.
I'm sure you know that you only need one dominant allele and two recessive alleles, so if you complete your punnet squares, you should have an accurate representation of your offspring.
If you have a Bb turquoise male and a bb leopard female, your offspring will be Bb, Bb, bb, bb. This means that half your offspring will be leopard, other half will be turquoise (about half). If you have BB and bb, your offspring will be all turquoise and Bb. This means they carry the leopard trait, but do not display it. So using the ratio of the offspring, you can track the alleles of the parents. Hope I helped!
Any questions? Sorry if I wasnt very clear.
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