Any biologists or geneticists around?

[hyphenate]

No, I'm not trying to start the eugenics war or anything, just want to check out a few things I was thinking about tonight. Please pardon any ignorance I might have on the topic, because the only genetics that I have much of a clue about are cats. Oh, and fruit flies. I believe that was Mendeleev. I could be horribly wrong, though.

Physical characteristics. I know what I've heard, but it really isn't much. I know the difference between a recessive and a dominant trait. I know that blue eyes are recessive, and that baldness allegedly follows from the maternal side. And of course, right handed people having a booming dominance over we lefties.

But what about other traits? What are other characteristics that are either recessive or dominant? I know heritage can be a major factor in health issues--that if a parent or further back relative had heart disease, chances are you have a higher percentage to get it than someone without that disease.

And I know that in the future, there could be a very good chance that "designer babies" could be a very real possibility. And that's where my questions lie.

Have scientists found out a great many traits which are either dominant or recessive? Let's say a mother has an oval face, and the father a square face shape, is there a better chance of the baby having an oval face, or a square face? What about hair color? (I will assume that my red hair is more rare than brunette hair, for example) Skin tone? In my own case, I look very Irish--red hair, green eyes, pinkish=white skin with a propensity for major sunburns, and a wee bit short. (Friends used to call me a leprechaun which incensed me a lot) And I would assume that I probably don't have much in the way of traits that someone from the Mediterranean might have. So I would assume that most of my relatives came from either the UK or Northern European countries, though you never know what might be hiding in your genes!

So I know that in my case, some dominant and some recessive traits were carried on through the egg-sperm dance in order to get me custom designed. But is there really a "switch" you can program that could make a person have specific traits--as long as they're somewhere in the family tree? (Yes, I know you probably can't inject some trait not found in the genes of the egg and sperm donors--or at least that's my understanding.) So could someone make decisions like: loves blue eyes, loves a straight nose, full lips, light brown hair, of high intelligence or superb athletic ability, skin that tans well and fights off skin cancer, and has an extraordinary ability to stay slim and firm. This, rather than someone with most of the opposite traits?

I know for the most part that this boils down to straight genetics, but if there are genes for competing traits, how are those traits distributed? Is it completely based on luck of the draw?

I keep using the word "know" above, so I might be completely wrong--if I am completely off-base, tell me gently.

[Rhiannon12866]

1. I don't have the answers, but have the same kinds of questions you have.

I lost my mother unexpectedly two weeks ago, so I've been thinking about these things, even though my mother had an accident. Certain illnesses do seem to run in my family, not to mention common physical traits, but my generation hasn't manifested any particular illnesses yet.

[Prism]

2. A simplified answer

When sperm and eggs are formed, there's a process called meiosis. This is when a parent's chromosomes duplicate themselves to form the sperm or egg cell. Before the sperm or egg are formed, the duplicated chromosomes split apart and intermingle with each other, creating unique genetic varieties. So even a sperm or egg alone will have a unique genetic make up different from the person who created it. So when fertilization occurs, you have a pretty unique genetic creature. (The odds of you and a sibling having the same genetic make up are one in 64 trillion). So there's no guarantee you're getting the same set of switches your parents have - you're only getting half their genetic material in a completely unique form.

Some characteristics are a straightforward dominant/recessive. One set of genes controls it, and you can figure out what will happen based on that dominant relationship (near-sightedness is an example). But there are also factors like codominant genes - genes that kind of split the difference (AB blood type comes from having the gene for type A and the gene from type B. Both genes combine to give AB). Codominant genes can also be partners in crime. Someone with two sickle-cell anemia genes will find the symptoms far more pronounced than someone with just one gene.

Then you have chromosomal genetic interplay. For example, with color blindness. Since the gene for it is on the X chromosome, males have no genes on their Y chromosomes to counteract it. Which is why males are more often colorblind.

So, the answer to your question, I guess is - it depends. If it's a simple dominant/recessive, it'd be more easily determined than, say, a genetic trait based on chromosomes. You can't switch a trait if there's nothing there to switch it with. And you can't do black/white traits if codominant genes are colluding to give someone the same characteristic.

I'm not sure I'm adequately explaining this, lol, but I hope it helps.

[DetlefK]

3. Genes aren't puzzle-pieces.

Of course there are some famous genes, because we see other peoples' eyes and hair colors all day. But don't forget that this comes from the tiny decision, which protein should be produced by the gene.

Mental traits and complicated body parts, like a nose, are way too large for a single gene.

For example, genetcis along my maternal line of ancestry:
My great-grand-mother was short, my great-grand-father was tall.
Grand-mother, grand-aunt and grand-uncle are tall. My grand-father was short.
My uncle tall, my mother short. My father short. (Most of my paternal relatives are short, except for two cousins of mine, who are tall.)
Me and my brother tall.

Good luck finding a mono-gene pattern in that.



And you have to discern between the genotype (genetic software) and the phenotype (hardware) representing a person. A person with black hair could have two genes for black hair, but he could as well have one gene for black and one gene for blonde hair. You can't determine the genetic code of an organism just by looking at it.

[Orrex]

4. Gene got married recently. HTH