Questions about gene-inheritance from parents

[Norbert]

First of all, let me just say that I am a total amateur at this. I know practically nothing. All I know is that each parent gives us 23 chromosomes and that there are something like 100000 genes altogether that determine who we become.

 

 

I am interested in how we inherit genes, and particularly genes that determine our more obvious characteristics from our parents. I am referring to noticeable characteristics like facial-bone structure/facial proportions, skin-color, hair-texture, body proportions and height as well as less obvious characteristics like blood-type, susceptibility to and/or immunity to certain diseases, etc.

 

Let me use a dramatic example, say a Japanese mother and an African father produce an offspring. The reason I chose this example is because there are obvious differences between their genes, judging by their physical differences. Okay, I know these differences are small but you can't deny them altogether. Their children would inherit half of their genetic information (23, right?) from their mother and the other half (the other 23, I'm guessing) from their father. These children would be perfectly bi-racial, half-Asian and half-black, unless crossing over would take place. Is this right so far?

 

Okay, now lets say one of these children met and married another person of first-generation bi-racial Asian/black ancestry and had children with them. Now it gets more complicated. The genetic information will get assigned randomly, from what I've read. These children will get some black and some Asian genes from their mother and some black and some Asian genes from their father. They can therefore be as much as ~100% Asian or ~100% black (theoretically) or anywhere in between. Is this right?

Edited February 19, 2012 by Norbert

[Essay]

They can therefore be as much as ~100% Asian or ~100% black (theoretically) or anywhere in between. Is this right?

 

On the most simple, theoretical level, that sounds like an valid understanding.

[Norbert]

On the most simple, theoretical level, that sounds like an valid understanding.

 

Good, at least I'm entering the room with a flickering candle I guess.

 

So how many genes actually determine who we become?

[Essay]

First of all, let me just say that I am a total amateur at this. I know practically nothing. All I know is that each parent gives us 23 chromosomes and that there are something like 100000 genes altogether that determine who we become.

....The bets were on when they sequenced the human genome, and many bets were for that range of 70-100k genes in our genome, so many were very surprised to see that we have far fewer genes than a corn plant ...or not much more than a mouse or chicken (iirc).

 

I think it is only about 20,000 genes that humans have (but I think that does not count the "junk DNA"), which is being found to be more than useless junk.

 

It may be up to 23,000 genes for humans, and on a DNA level we are very similar to chimps; but on the level of how those genes are arranged, and when they are activated during development, and for how long they are activated or at what concentration they are activated, there is a lot of room for differing end results. Some genes are used once (during development) for building the digestive system, and then later during development for building the brain system. Some genes get duplicated, and the original gene retains the function while the duplicate is allowed to mutate and experiment with new functions. ANd then there is also epigenetics (something to google).

There are many ways that the same genes can produce varied creatures, and when you also add different genes (even just a few) in the right place and at the right time in a creature's genome, then you get some unique and marvelous "new" species.

 

With just a few handfuls of letters, we build an extensive dictionary--out of which many different novels, treatises, poetry and prose, eventually evolve.

 

Sean B. Carroll likens the genome to an artist's palette, where a few colors can be mixed and matched in time and space to create many different compositions.

 

Google: Sean B. Carroll and "Endless Forms Most Beautiful" to catch a great lecture.

...or any lecture by him would be worthwhile i bet....

 

~

Edited February 21, 2012 by Essay

[ewmon]

I think some of the best empirical data to consider for your biracial × biracial "cross" involves Afro-Americans. From your supposition, we would expect to see at least a few Afro-American couples giving birth to ~100% African or ~100% European children, when in fact, we don't see such offspring. About 1 in 6 Americans is Afro-American, so we're talking 50 million Afro-Americans and tens of millions of Afro-American couples.

 

And I'm pretty sure the reason is because most of the traits we consider "racial" don't combine as dominant/recessive traits, if my memory serves me correctly, so we're not going to see Mendelian genetics at work.

[Essay]

I think some of the best empirical data to consider for your biracial × biracial "cross" involves Afro-Americans. From your supposition, we would expect to see at least a few Afro-American couples giving birth to ~100% African or ~100% European children, when in fact, we don't see such offspring. About 1 in 6 Americans is Afro-American, so we're talking 50 million Afro-Americans and tens of millions of Afro-American couples.

 

And I'm pretty sure the reason is because most of the traits we consider "racial" don't combine as dominant/recessive traits, if my memory serves me correctly, so we're not going to see Mendelian genetics at work.

 

Of course, in the real world, your points are completely correct. The phrasing of the OP suggested an answer on the level of "On the most simple, theoretical level...." I assumed race was only used in the OP as a random example of "gene-inheritance from parents," and I hope this doesn't end up in the sociology or politics forum.

~

[Norbert]

I assumed race was only used in the OP as a random example of "gene-inheritance from parents,"

 

That is correct.