We don't get 50/50 of distinct genes from our parents - it is more like 30/70 and can be even 10/90. The whole DNA ratio in this equation is irrelevant, as we all have 99% of the same DNA. Also, in real world, one parent will consistently give more of their distinct genes than other parent and most likely that consistent gene part will have that single mutation that they would hope to avoid, but contain best genes that the parent can offer. Children from multiple partners could be a solution as it is a different math...
>>>There are also medical procedures (PGD) to bring that chance to virtually 0%.
For that one gene only.
DNA is a math of sum of genes and from what I have read humans are not better than nature(which is not perfect, but very basic) at selecting best specimens of eggs and sperm, but yes - whatever they have picked - PGD might be able to root out that one single mutation, and introduce variety of other mutations or miss good genes from other combinations. So, it all depends...