No, I am not using the hybrids to produce a milder fish. I do have another reason for these hybrids, but can't discuss it here. For the purpose of this topic (domesticating the Gambusia), hybrids will be used to determine how many dominant genes are involved in Gambusia aggression.
The way it will work is like this - I cross Gambusias with another non-aggressive species. Since they get a full set of chromosomes from each parent, these first-generation hybrids will all be aggressive. However, each dominant aggression gene they inherited from their Gambusia parent will be paired with a recessive non-aggression gene from the other parent.
Now, of these first-generation hybrids, a small percentage will (hopefully) not be sterile. I will cross these individuals back to the non-aggressive species. These second-generation hybrids will randomly inherit either dominant aggression genes or recessive non-aggression genes from their first-generation hybrid parent, and of course recessive non-aggression genes from their other parent.
Now I count how many of these second-generation hybrids are aggressive. The ratio of aggressive to non-aggressive can be plugged into a simple formula to calculate how many dominant aggression genes there are. This method will not count recessive or co-dominant aggression genes if there are any.
This information is mainly just to satisfy my curiosity. The domestication project will only involve pure Gambusia lines, not hybrids.
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