[foreigner]

We get half of our genes from each of our parents. So unless this person has the extremely unlikely misfortune of partnering with someone else with the same rare mutation, their offspring would only have a 50/50 chance of inheriting their copy of this gene. There are also medical procedures (PGD) to bring that chance to virtually 0%.

[something098]

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...

[Sammi]

Also parents who are both carriers have a 25% chance of making a sick child, a 25% chance of making a non carrier and non sick child, and a 25%+25% chance of making non sick yet carrier child. So they already have a 50% chance of making children who'll survive and yet be carriers of the disease. I guess this will increase this to 75%. But you have to evaluate this in connection with the rapid increases in genetic treatment options, which decreases the issues.