I understand your concerns. I was just pointing out that what you worry about isn't uncommon and rarely the reality.
DS also has expressions and traits I share. It isn't genetic. And yet in so very many ways he is so much like a mini-me that it makes my mum laugh.
You really do forget how your child became your child at various points, it really isn't something you think about much after a certain point. My mum at one point said to me "DS really has your hair doesn't he?" and looked very confused when I said "Actually no he really doesn't".
I have even fallen into the trap of it myself when joking with someone about how I used to be a man (long story why it was a joke) when they said "well I know that's not true because you have your lovely DS" and I genuinely said "Duh yes of course that gives it away" totally forgetting that it proves nothing!
Maybe its a bigger issue if you do spend a lot of time pointing out your child has your nose/chin etc but the majority of adopters I know have birth children and really its doesn't impinge on their lives the majority of the time.
In any event when you have children who look very dis-similar to you (as DS does to me - different race/colour/sex) whether because they are step children, adopted, mixed race, or just look very different, there is a lovely book by Carrie Kitse "I don't have your eyes"... but I have your way of looking at things.
Other examples "I don't have your hair ... but I have your way of letting it down"
"I don;t have your feet... but I have your way of taking things one step at a time"
Its a really beautiful book for any children who look different to their parents and really encourages you as a parent to focus on the things that you and your child have in common not in the visual differences (it does celebrate difference too "I don't have your face but I know you love the look that is mine alone".
My point wasn't that you didn't or shouldn't worry about it but that its normal to worry about any number of things with a second - believe me the worry isn't less adopting a second because they aren't genetically related but more with the added risks of drug addiction, foetal alcohol syndrome and unknown inherited illnesses without factoring in the almost certain damage done by the process of adoption itself. My point was more that the worries we all have about prospective unknown children aren't always rational and even if they are rational, you can deal with them without too big an impact.