Reproduction: would you have been 'You' a month later?

Factual Questions
1

Here’s one I’ve always pondered.

Would the current 'persona known as ‘where’s the subscription info’ have been the same ‘where’s the subscription info?’ if my Ma & Pa had messed up the sheets a month later than they did? Y’know, same sperm doner but different egg?

… or a different aspect of the same query. Did it matter which of Pa’s little wriggles happened upon the egg to beget me? i.e. if one of my* brother sperm had pipped me to the post, would I be the same me? Or is each different sperm a slightly different set of genes/DNA.

  • Geddit? Clever eh?
2

Each egg and each sperm are different genetically. That’s why we’re different than our brothers and sisters. So, if a different sperm had fertilized the same egg or vice vers, you would have been genetically different than you were.

3

If all sperm and ova were the same, all siblings would be identical twins.

You are you only because a particular sperm and ova happened to meet up and get together. Any different parts would have different DNA and be a different person.

4

[QUOTE=where’s the subscription info?]

Did it matter which of Pa’s little wriggles happened upon the egg to beget me?
[/QUOTE]

Yep. Genetically, anyway. Human DNA has 23 pairs of chromosomes. Each pair consists of one chunk from Mom and one from Dad. But mom and dad both have their 23 pairs each as well. When gametes (sperm and egg cells) are formed, each one contains 23 randomly selected single chromosomes. For example, one particular sperm cell may have side A of chromosome 1, and side B of chromosome 2, while another sperm cell has side A of both chromosomes 1 and 2, and so on, for every possible permutation.

The same thing happens with eggs. When a sperm meets an egg, the half-pairs from each combine to make up the genome of the fetus.

So when a given sperm meets a given egg, there are four possibilities (AA, AB, BA, BB) for each of the 23 pairs to come together. That’s a lot of genetic shuffling. (There are also other processes that introduce further randomness into the process, such as mutations.)

This, by the way, is why you are not identical to your siblings. Also, the 23rd chromosome determines your sex: (It’s the only one whose halves are named X and Y.) Females have two X chromosomes, so all eggs will have one X. Males have an X and a Y, so a sperm cell will randomly have either an X or a Y. Ergo, the fetus will end up with XX or XY depending on which sperm cell wins the race. (Again, there are complications like XXY and XYY conditions that occur rarely.)

5

[QUOTE=friedo]
Yep. Genetically, anyway. Human DNA has 23 pairs of chromosomes. Each pair consists of one chunk from Mom and one from Dad. But mom and dad both have their 23 pairs each as well. When gametes (sperm and egg cells) are formed, each one contains 23 randomly selected single chromosomes. For example, one particular sperm cell may have side A of chromosome 1, and side B of chromosome 2, while another sperm cell has side A of both chromosomes 1 and 2, and so on, for every possible permutation.

The same thing happens with eggs. When a sperm meets an egg, the half-pairs from each combine to make up the genome of the fetus.

So when a given sperm meets a given egg, there are four possibilities (AA, AB, BA, BB) for each of the 23 pairs to come together. That’s a lot of genetic shuffling. (There are also other processes that introduce further randomness into the process, such as mutations.)

This, by the way, is why you are not identical to your siblings. Also, the 23rd chromosome determines your sex: (It’s the only one whose halves are named X and Y.) Females have two X chromosomes, so all eggs will have one X. Males have an X and a Y, so a sperm cell will randomly have either an X or a Y. Ergo, the fetus will end up with XX or XY depending on which sperm cell wins the race. (Again, there are complications like XXY and XYY conditions that occur rarely.)
[/QUOTE]

<hijack>
but related.
How far advanced is the state of genetic screening/counseling today? I want to have kids, but have some genetic conditions I don’t want to pass on. Are some of my little critters (sperm) different than others? Can they (reproductive specialists) screen and filter out those critters that are carrying the bad gene, and turkey-baste (implant) the non-bad-gene ones into the woman’s egg? Is there any *en vivo * drug or procedure to kill the bad critters, & leave the good ones intact? I’m dying to have kids naturally, but only if I’m reasonably assured I’m not passing on the bad genes. Finally, if I inherited the bad genes from my mother, does that mean all my X-critters could be zapped or incapacitated, leaving the Y ones intact, thus guaranteeing a boy? The desired end result is, the kid who would’ve been born with the bad genes never gets conceived, and his healthier sibling does.
</hijack>

6

Also, I would expect that tiny changes in how you develop create a unique “you” in terms of the you that is the sum of the mesh of neurons in your brain, even if the DNA where to be identical.

So even if the same sperm and egg met, it’s likely that ANY differences in time would lead to a different “individual personality”, if you get my meaning. Perhaps you would have been a replublican opera lover instead of what you currently are.

7

Only if the genes in question are on the X chromosone. Most of them aren’t. The genes for hemophilia and colorblindness are on the X, but I can’t think of any others (aside from ones directly related to sex) off the top of my head.

For the rest of your question, it’s certainly possible in principle, but I don’t know if we have the technology to test the genes in a sperm cell, and then put it back together well enough to fertilize an egg.

8

[QUOTE=Chronos]
Only if the genes in question are on the X chromosone. Most of them aren’t. The genes for hemophilia and colorblindness are on the X, but I can’t think of any others (aside from ones directly related to sex) off the top of my head.

For the rest of your question, it’s certainly possible in principle, but I don’t know if we have the technology to test the genes in a sperm cell, and then put it back together well enough to fertilize an egg.
[/QUOTE]

Think I understand your point on ‘Only if the genes in question are on the X chromosone’. So just because my mother had the same condition I have, that don’t mean my ‘x’ genes are carrying it? It could be a recessive, long-dormant-but-awakend-in-me gene from my father (my ‘Y’ chromosome)? If that’s true, then there’d be no point killing off all the ‘x’ critters (sperms), but rather, test a batch of either ‘x’ or ‘y’ if they’re carrying the bad gene - and thus could have a healthy daughter too. In short, I can’t assume since I inherited the condition from my mother, the bad gene must be on my ‘x’ chromosome?
Finally, does anyone know what options are available for gene filtering?

9

Or it could be from your mother, but on one of the other 22 chromosomes. For all of those other chromosomes, there’s no way to tell which of your pair came from your father and which came from your mother, other than getting samples from your parents and comparing. If you have some troublesome genes, then you’d need to look for those genes themselves, not just “mother genes” and “father genes”.

10

[QUOTE=volleyballer]
<hijack>
but related.
How far advanced is the state of genetic screening/counseling today? I want to have kids, but have some genetic conditions I don’t want to pass on. Are some of my little critters (sperm) different than others? Can they (reproductive specialists) screen and filter out those critters that are carrying the bad gene, and turkey-baste (implant) the non-bad-gene ones into the woman’s egg? Is there any *en vivo * drug or procedure to kill the bad critters, & leave the good ones intact? I’m dying to have kids naturally, but only if I’m reasonably assured I’m not passing on the bad genes. Finally, if I inherited the bad genes from my mother, does that mean all my X-critters could be zapped or incapacitated, leaving the Y ones intact, thus guaranteeing a boy? The desired end result is, the kid who would’ve been born with the bad genes never gets conceived, and his healthier sibling does.
</hijack>
[/QUOTE]

You are a male so you have an X chromosome from your mother and a Y chromosome from your father. Your partner (a female) will have 2 X chromosomes.
So when you reproduce, your partner will contribute an X and you will contribute either an X or a Y. If you contribute an X, you will have a girl (XX) and if you contribute a Y, you will have a boy (XY).

If you truly have an X-linked genetic disorder, you will need to see a reproductive endocrinologist before having kids. You have a couple of options: you could ‘sperm spin’ and separate out all the sperm with Y chromosomes. Then you can “turkey baster” the Ys into your partner (aka Intrauterine insemination) and impregnate her with a boy OR you can do invitro. If you do invitro, there is a process called PGD (pre genetic diagnosis) where they can test the embryos before implant and make sure there are no genetic problems.

11

[QUOTE=Enola Gay]
You are a male so you have an X chromosome from your mother and a Y chromosome from your father. Your partner (a female) will have 2 X chromosomes.
So when you reproduce, your partner will contribute an X and you will contribute either an X or a Y. If you contribute an X, you will have a girl (XX) and if you contribute a Y, you will have a boy (XY).

If you truly have an X-linked genetic disorder, you will need to see a reproductive endocrinologist before having kids. You have a couple of options: you could ‘sperm spin’ and separate out all the sperm with Y chromosomes. Then you can “turkey baster” the Ys into your partner (aka Intrauterine insemination) and impregnate her with a boy OR you can do invitro. If you do invitro, there is a process called PGD (pre genetic diagnosis) where they can test the embryos before implant and make sure there are no genetic problems.
[/QUOTE]

Thanx, E.G. - this is the direction I was looking for.
From previous posts, I interpret that I can’t assume that because I inherited a condition from my mom, that the defective gene must be on my ‘x’ chromosome (and therefore, the ‘x’ sperm). So the 1st step would be finding out where the defective gene is.
Reproductive endo, or another specialist (urologist)? Would they do a blood or a sperm test, if my concern is passing it onto kids? Finally, if it is X-linked, is there any conceivable way (pun intended) to create a defect-free daughter, *a la * ‘cooking’ the defective ‘x’ sperm, to rid it of its defect (like, swapping out the defective chromosome with one from a ‘y’)?

12

I can’t see how I would possibly be me if I were born with a different genotype. The “me” that I am is the result of the interaction of my environment with my genes, so a difference in either would result in a different “me”. The differences might be small, say if I were born with a different eye or hair colour or they could be massive, say if I were born female.

13

[QUOTE=volleyballer]
Thanx, E.G. - this is the direction I was looking for.
From previous posts, I interpret that I can’t assume that because I inherited a condition from my mom, that the defective gene must be on my ‘x’ chromosome (and therefore, the ‘x’ sperm). So the 1st step would be finding out where the defective gene is.
Reproductive endo, or another specialist (urologist)? Would they do a blood or a sperm test, if my concern is passing it onto kids? Finally, if it is X-linked, is there any conceivable way (pun intended) to create a defect-free daughter, *a la * ‘cooking’ the defective ‘x’ sperm, to rid it of its defect (like, swapping out the defective chromosome with one from a ‘y’)?
[/QUOTE]

Medical technology can’t currently target a specific chromosome within a single cell and replace it with another one.

Also, chromosomes from your mom don’t neatly sort themselves into X sperm, while dad-derived chromosomes go into Y sperm. The groupings are completely random. One of your sperm might have chromosome 1 from Mom, 2 from Mom, 3 from Dad, 4 from Mom, 5-8 from Dad, etc. (I’m ignoring the concept of crossing-over here, and thus oversimplifying, but you get the idea.) Google ‘independent assortment’ to learn more.

X-linked means that the gene in question is PART OF the X chromosome, not that it came from Mom. The reason you hear about it is because there are some genes that are only on the X chromosome, but not on the Y, which is kind of small. Therefore, girls have two copies of these genes (because they have two X’s, one from Mom, one from Dad), while boys have only one. If there’s a recessive problem with one of the genes on the X chromosome, if the child is a girl, usually that’s not a problem, because she’s got her second X chromosome with another copy of the gene that probably doesn’t have that problem. But if the child is a boy, well, he’s got no backup. That’s why X-linked diseases are more common in boys. That said, the vast majority of genes aren’t on the X chromosome, aren’t passed down in an X-linked fashion, and aren’t really relevant to the question you’re asking.

The short answer to your questions is that nowadays, doctors can make a bunch of embryos by mixing your sperm with eggs from your partner (or a donor, I suppose). They can then wait until the embryos grow to about 8 cells, at which point they remove one or two and test them for whatever disease genes you’re afraid of passing on. (This does not harm the embryos.) They can then select out the embryos without those genes and implant them in the prospective mother. This technique is called preimplantation genetic diagnosis (PGD, or PIGD). It does NOT work by tweaking your sperm before making the embryos. Of course, this is insanely expensive and only done in relatively rare cases, for particular types of severe diseases. If you are only looking to tilt the odds in favor of making a baby of a particular gender, there are ways to sort sperm, then artificially inseminate with mostly X sperm or mostly Y sperm, but although this is much cheaper, it’s not foolproof.

14

[QUOTE=GilaB]
Medical technology can’t currently target a specific chromosome within a single cell and replace it with another one.

Also, chromosomes from your mom don’t neatly sort themselves into X sperm, while dad-derived chromosomes go into Y sperm. The groupings are completely random. One of your sperm might have chromosome 1 from Mom, 2 from Mom, 3 from Dad, 4 from Mom, 5-8 from Dad, etc. (I’m ignoring the concept of crossing-over here, and thus oversimplifying, but you get the idea.) Google ‘independent assortment’ to learn more.

X-linked means that the gene in question is PART OF the X chromosome, not that it came from Mom. The reason you hear about it is because there are some genes that are only on the X chromosome, but not on the Y, which is kind of small. Therefore, girls have two copies of these genes (because they have two X’s, one from Mom, one from Dad), while boys have only one. If there’s a recessive problem with one of the genes on the X chromosome, if the child is a girl, usually that’s not a problem, because she’s got her second X chromosome with another copy of the gene that probably doesn’t have that problem. But if the child is a boy, well, he’s got no backup. That’s why X-linked diseases are more common in boys. That said, the vast majority of genes aren’t on the X chromosome, aren’t passed down in an X-linked fashion, and aren’t really relevant to the question you’re asking.

The short answer to your questions is that nowadays, doctors can make a bunch of embryos by mixing your sperm with eggs from your partner (or a donor, I suppose). They can then wait until the embryos grow to about 8 cells, at which point they remove one or two and test them for whatever disease genes you’re afraid of passing on. (This does not harm the embryos.) They can then select out the embryos without those genes and implant them in the prospective mother. This technique is called preimplantation genetic diagnosis (PGD, or PIGD). It does NOT work by tweaking your sperm before making the embryos. Of course, this is insanely expensive and only done in relatively rare cases, for particular types of severe diseases. If you are only looking to tilt the odds in favor of making a baby of a particular gender, there are ways to sort sperm, then artificially inseminate with mostly X sperm or mostly Y sperm, but although this is much cheaper, it’s not foolproof.
[/QUOTE]

Thanx Gila.
To simplify, I’ll simply spell out it’s metabolic syndrome, atherosclerosis, & diabetes. Definite yes on the 1st 2, no on the 3rd, for me so far. Same for my sister. My mom’s family has a pretty convincing propagation, men and women, and none in my father’s - hence my assuming we got it from Mom.
So, if my goal is simply not to pass these on to any kids (I’d be thrilled with either boys or girls), the only way is to do this is the preimplantation genetic diagnosis? No chromosomal fixing, on the sperm or zygote level? Finally, as long as they’re testing for these 3 (if they can target them), do they do a whole battery of tests, for all serious possible defects?

15

Forget genetics, I don’t think you would have been you if you had been burped a few times less.

16

[QUOTE=volleyballer]
Thanx Gila.
To simplify, I’ll simply spell out it’s metabolic syndrome, atherosclerosis, & diabetes. Definite yes on the 1st 2, no on the 3rd, for me so far. Same for my sister. My mom’s family has a pretty convincing propagation, men and women, and none in my father’s - hence my assuming we got it from Mom.
So, if my goal is simply not to pass these on to any kids (I’d be thrilled with either boys or girls), the only way is to do this is the preimplantation genetic diagnosis? No chromosomal fixing, on the sperm or zygote level? Finally, as long as they’re testing for these 3 (if they can target them), do they do a whole battery of tests, for all serious possible defects?
[/QUOTE]

The problem with preventing any offspring from having many disorders is that we as of yet don’t completely understand how they are inherited. We can screen for diseases such as Tay-Sachs disease or cystic fibrosis because they are a result of mutations in a single gene, and if you inherit two copies of the mutated gene (or one copy in some diseases), you will have the disease.

Diseases such as atherosclerosis and diabetes are more complex. In most cases, there seems to be an interplay of multiple genetic and environmental factors causing the disease. For example, having family with Type II diabetes predisposes you to developing diabetes but does not guarantee that you will. On the other hand, you can also modify your risk (ie by keeping your weight under control).

So PIGD is a good option for people who know they are carriers of single-gene disorders, but for the more common multifactorial diseases not enough is known yet to justify it for them.

17

Even apart from the genetics, a month can make a difference.
I was born in September, a swing month for school grade level. If I was born a month later, I would probably have been put into the class behind me (class of 1997 instead of 1996). I suspect I would be a very different person if that were the case, even with the same egg and sperm. Different friends, oldest in class instead of youngest, etc.

18

[QUOTE=Hirundo82]
The problem with preventing any offspring from having many disorders is that we as of yet don’t completely understand how they are inherited. We can screen for diseases such as Tay-Sachs disease or cystic fibrosis because they are a result of mutations in a single gene, and if you inherit two copies of the mutated gene (or one copy in some diseases), you will have the disease.

Diseases such as atherosclerosis and diabetes are more complex. In most cases, there seems to be an interplay of multiple genetic and environmental factors causing the disease. For example, having family with Type II diabetes predisposes you to developing diabetes but does not guarantee that you will. On the other hand, you can also modify your risk (ie by keeping your weight under control).

So PIGD is a good option for people who know they are carriers of single-gene disorders, but for the more common multifactorial diseases not enough is known yet to justify it for them.
[/QUOTE]

Yeah, my doctor’s favorite slogan is ‘genetics loads the gun, & lifestyle pulls the trigger’. :rolleyes: However, having received a shocking lesson ex post facto, I’m trying to stack the deck in the [as yet unconceived] kid’s favor.
There’ve already been some serious consequences for me, tho no sign of diabetes yet. So, to wrap up, the only ways to be sure not to pass on the predisposition to (if not actual) disease, like metabolic syndrome & atherosclerosis, are:
a) adopt
b) disease-free sperm donor
c) p.i.g.d., and toss out any defective zygotes (even tho lifestyle choices can delay onset, the predisposition is still there).
No genetic screening can yet pre-filter out non-single-gene linked disorder. Anything new & exciting expected in the next 5 years?

19

[QUOTE=volleyballer]
Thanx Gila.
To simplify, I’ll simply spell out it’s metabolic syndrome, atherosclerosis, & diabetes. Definite yes on the 1st 2, no on the 3rd, for me so far. Same for my sister. My mom’s family has a pretty convincing propagation, men and women, and none in my father’s - hence my assuming we got it from Mom.
So, if my goal is simply not to pass these on to any kids (I’d be thrilled with either boys or girls), the only way is to do this is the preimplantation genetic diagnosis? No chromosomal fixing, on the sperm or zygote level? Finally, as long as they’re testing for these 3 (if they can target them), do they do a whole battery of tests, for all serious possible defects?
[/QUOTE]

Disregard my response above because I completely misunderstood you and thought you were referring to a specific genetic disorder (I had pgd for one). Anyway, what GilaB said is true but AFAIK PGD cannot screen for diabetes (not even type 1) or atherosclerosis. Not sure what metabolic syndrome you are referring to so I can’t say on that. Your best bet is to see an RE and get a proper diagnosis and genetic workup.