What traits get passed on to your kids

My question is pretty specific.

My friend (F*rd) was born without incisors (the sharp teeth near the front). So, if he has kids, will they be likely to inherit this trait, or unlikely? I understand that some things skip a generation and others are not genetic.

My reason for asking is, a mutual friend of Furd and I, who is married to someone who is not Ford has a child who is about 8 years old now, and seems to have this trait.

Fyrd was around about 9 years ago, and maybe had opportunity to have a fling with the child’s mom. How much of an indicator is this trait of paternity?

Hard to say in your friend’s particular case. Most mutations are recessive, so if this is due some random mutation, it is likely that the other parent will provide the necessary allele for incisor teeth. Of course, it’s possible that this is a non-recessive mutation and your friend will pass it on to the next generation. It’s also possible that the lack of incisors is not genetically based, in which case the kids are home free.

Thank you John Mace. So, it seems that there is a little uncertainty in whether this is passed on father to child.

Does anybody have any different ideas?

Yes, your friend’s children will be born without incisors.

And so will yours.

And so will mine.



That was great. I was sure that you were offering me some great insight into genetic science, when it finally hit me.

Espcially because when you mentioned my kids, my paranoia had me thinking that this guy had been playing around with my wife…

But, then I realized he had never met your wife (or you?), so my logic fell apart.

For most traits, it doesn’t matter at all which parent (mother or father) has it. There are a few sex-linked traits such as hemophilia and color-blindness which are carried on the X chromosone and which are therefore more commonly expressed in men. But there are 22 other chromosones a gene could be on, which aren’t sex-linked.

Now, I don’t know what the genetic basis (if any) is for the “no incisors” trait, so I can’t say exactly what will happen. But I can cover the different cases. For simplicity, I’ll assume that this is governed by a single gene, and that we don’t have any mixed dominance going on.

Case 1: No-tooth is caused by a recessive gene. This means that Fard has two copies of the gene, or else the trait wouldn’t show.

Case 1a: Ferd’s wife does not have any copies of the gene (the most likely case, assuming that we’re not diving into the shallow end of the gene pool). In this case, all of Fird’s children will have one copy of the no-teeth gene, and one copy of a normal teeth gene. Since we’re assuming for the moment that the no-teeth gene is recessive, this means that the kids will have their teeth. But if one of them mates with someone else with this gene, then some of Fwrd’s grandchildren might show the no-teeth trait. The first generation of children are called carriers of the gene, even though they don’t show it.

Case 1b: Fùrd’s wife has one copy of the gene. She’s a carrier, but doesn’t show the no-teeth trait. In this case, half of the children will get two copies of the no-teeth gene, and therefore will show the trait. The other half will be carriers.

Case 1c: Förd’s wife, like himself, has two copies of the no-teeth gene and is therefore missing teeth. In this case, all of the children will receive two copies of the no-teeth gene, and the whole family is going to look pretty funny when they smile for family photos.

Note that we can get people who carry a recessive gene, but do not show the trait. You could even have two carriers as parents, both of whom appear normal, but who have a child who shows the trait. This is what’s happening when a trait “skips a generation”. There’s still a chance that it’ll show up after a single generation, and there’s also a chance that it’ll stay hidden longer, or that the children won’t carry the gene at all.
Case 2: The no-teeth gene might be dominant. In this case, all we know about Frrd’s genes is that he has at least one copy of the no-teeth gene

Case 2a: F!rd has two copies of the no-teeth gene. No matter what genes his wife has, all of his children will get at least one copy of the gene (definitely one from him, and maybe also one from their mother if she’s a no-toother). Since you only need one copy of a dominant gene to express a trait, this means that all of the children will have the no-teeth trait, but their children may or may not (see next case).

Case 2b: F@rd has one copy of the no-teeth gene, and his wife has none. Half of the children will inherit one copy of the no-teeth gene and be just like their father, and half of them will not, and they (and their descendants) will be completely normal in this regard.

Further cases are left as an exercise for the reader.

We could rule out some of these cases, if we knew anything about F[symbol]h[/symbol]rd’s family. For instance, if neither of his parents shows the no-teeth trait, then we know that the gene for it can’t be dominant. And if his wife has normal teeth, then we can rule out case 1c. We could also make some guesses, if we knew about the grandparents, cousins, aunts and uncles, etc. Do we have any more information?

The other important case you left out is that the trait is controlled by multiple genes, which is not uncommon. In that case, it’s tougher to predict what will happen with the kids.