They don't "lose" genetics, but if you don't keep the conditions pretty close to EXACTLY as they were for the previous cycle there will be a difference. People will argue this to the death. There are different amounts of hormones in different areas of the plant. Clones from lower on the plant have higher levels of these hormones, and ones taken from higher have lower levels. So, in theory, the ones from lower on the plant will give you a better success rate. Your plants are changing if you notice it or not.