Genetics is way more complicated than science is willing to admit. l
Take for example someone's eye color? You can't just go in and switch a gene and get blue eye's. Doing that would only give you a slightly higher chance of having blue eyes. It takes changing a few genes to get blue eyes in humans. But by changing so many genes, you inadvertently change other things as well. One of which is sexuality.
Price cattle farmers have known for decades now that the chance of getting a hetero bull from a genetically altered specimen is about 50-50.
But also look at everything that is genetically encoded that's not obvious. Like the coding for your sense of smell. Some people have lost the sense to smell pheromones from other humans. But oddly enough, they can smell the pheromones from apes.
Another example is taste, some people are genetically wired to taste Cumin like soap or a strong poison. While others taste it like a sweet flavor.
Another example is your sight. You get your spectrum of colors from your parents, but we all don't see the colors the same shades. Because somewhere down the genetic tree, those who didn't need to see a certain color, lost the ability to see it correctly.
But in labs all over the world, they have known for a long time that messing with the code of many animals and insects have a super high chance of producing gay results. Such as designing a labrador retriever with blue eye's. He will have blue eyes and be gay. But you can genetically make one that glows in the dark and its hetero. Go figure.