My wife and I have a beautiful 11 month old son who resembles a little of both of us in his features. How much of our genes are ours as compared to those we inherit from our parents and granparents ? (Like, why did he get my eyes and her nosebut his chin is from neither…) Also, what tells your genetics to be a certain way, i.e. green eyes,red hair or blue eyes,blonde hair ?
All of your child’s genes come from you and your wife – half from you and half from her. Just like all of your genes came from your parents. How the genes express themselves depends on what combinations they end up in.
so…he would not get genes that were “created” just for him ? all of his genes are derivatives of ours ?
Unless your son was involved in a massive “breeding scheme” like the Bene Gesserit in Dune for the Kwisatz Haderach (I digress), there is no likelihood of any genes “created” or “planned” for him.
As for what decides features… it really boils down to randomness. When the sperm and the ovum fuse together, the genetic material fuses as well. Some information are “dominant” and get expressed externally. For example, a sperm carries the information for “brown irises” and the ovum has the information for “blue irises”, but the baby has brown eyes. Why? Because!
Other traits like height, facial features would be dependent on many genes and even the environment, so this could explain why your son’s chin does not resemble that of you or your wife.
yes, all his genes are from you. All your genes are from your parents.
But this gets complicated in the process.
You pass on genes on chromosomes. Half your set goes to the kid, half the other parent’s set goes to the kid. But the exact sets get mixed around a bit, so you aren’t passing on to your son the same set you got from your father - you’re passing on a mixed set from both parents. So while your child will resemble you and your wife, there’s enough combinations at play that they end up looking unique.
Add in the expression of genes that had been hidden a while (due to the exact combinations each person got) and you get what we’ve got - a son who looks like a cross between my husband and my father, but who has a dimple in his chin - something we’ve not seen in either family for as far back as we have pictures.
here’s a good basic concepts education in how genes work, including the whole combination process (follow the links on the right side to get to each topic)
The above is true of course, but I think mention of crossing over may be warranted here. Let’s see if I can explain this simply.
Each cell in your body has 23 pairs of chromosomes (or 46 individual chromosomes). One member of each pair was gotten from your mother and one from your father. However, when you make sperm, the sperm only has 23 individual chromosomes, and those individual chromosomes are a mixture of the ones you got from your mother and those you got from your father. Only one member from each pair is selected, and the selection is random. This selection happens during sperm formation, also known as meiosis.
What’s more is that the chromosomes will even swap genes during meiosis. The maternal/paternal pair of chromosomes will exchange sections of themselves just before one is randomly selected to be the genetic compliment passed on via the sperm (or the ova in your wife’s case). This is called “crossing over” and means that the chromosome you got from your mother or father is not the same chromosome you pass on to your kid. You pass on a mixture of the two. This helps nature to shuffle the deck very fine.
The genes are still the same ones you inherited, but the chromosomes aren’t. This can sometimes even add diversity (sort of) by shuffling gene sets. Sometimes a new trait will arise because a new set of genes has been created.
Inheritance isn’t always a single gene equation - sometimes it is a multigene complex. If crossing over produces a new complex with a different multigene set, the offspring may exhibit a trait not shown in either family up to that point. However, unless there has been a mutation, there won’t be any new genes.
I will leave it here for now, though I may return later and discuss how traits can skip generations due to recessive genes or even appear out of the blue entirely due to recessive or “partially recessive” genes.
I declined to go into crossing over, as it was covered in the link… and I couldn’t figure out how to explain it concisely! Thanks, good job. 
I often wonder whether the whole chin dimple is a simple recessive or a multi-gene trait…
:rolleyes: (what a geek)