Generations of Clones

I have an eerie feeling I’ve asked this before, but searching is revealing nothing, so I hope that was in a dream, sorry in advance if that’s the case.
So, here’s my disturbing question of the day:

Let’s assume we have a male human, let’s call him Bob. Now, assume we have some sort of a magic cloning technology that let’s us clone Bob entirely, but instead of his regular XY pair, duplicate his X chromosome and make an XX pair with both X’s being identical (Hopefully this doesn’t break some cardinal rule in genetics, although I understand that it makes a person slightly more susceptible to genetic disorders). Let’s call our XX clone of Bob, Jane (since she’s obviously female).

Now, consider Bob and Jane’s children. The way I see it, they’ll either be genetic clones of Bob or genetic clones of Jane (who are, for all intents and purposes just differently equipped versions of each other), correct? Now if grandchildren also interbreed, they will keep making the same copies of Bob and Jane (disregarding mutations for a moment). So for a few generations you will have copies of the same individuals, right?

Now, say the original premise is true and it’s possible to make a female clone of a male individual (or will be possible some day). Is this a feasible way to make a large number of copies of the same individual with minimal intervention? How bad are the genetic problems associated with complete lack of diversity like this? Am I missing something crucial here…
evil laughter
Thanks,

Groman

Okay… well, let’s simplify and look at one of the sex-undifferentiated chromosomes. Humans have a whole bunch, can’t remember the exact number, and either one or two carry the XX/XY genes that determine gender.

okay, for chromosome 12, bob has two different gene sequences on this chromosome… all animals that reproduce sexually have two different sequences, our chromosomes are paired. Let’s say that one sequence is AAAAABBBBBCCCCC, and the other is ABCDABCDABCDABD.

Since Jane is a perfect clone except for the sex-linked genes, she has the same sequences on her chromosome 12.

Now, when Bob and Jane have, the children will usually get one gene sequence from each parent in each chromosome, chosen randomly. That means that they are quite UNlikely to be clones of either of their parents. A kid has a 50% chance of getting both sequences on their chromosome 12, but they also have a 50% chance of getting the same sequence, duplicated.

And, let’s just say that the D at the end of the ABCDABCDABCDABD sequence indicates a recessive genetic disorder. For both Bob and Jane, the gene was masked by their C gene on the other sequence, because it’s recessive. Any kid unlucky enough to get two copies of the ABCDABCDABCDABD sequence gets that genetic disorder though.

Now, sometimes genetic sequences are not passed on exactly as they were received by the parents… you can get single bit errors (which would turn AAAAABBBBCCCC into AAAAABCBBBCCCC,) or sequence switching, (which could turn the above sequences into AAAAABBBBBCDABD and ABCDABCDABCCCCC.) But the general point holds.

Now, if you’ve genetically engineered Bob so that he’s viable with identical gene sequences on all of his chromosomes, (and a swell guy to boot,) then your scheme could work… something like that was mentioned in Anne McCaffrey’s ‘Sassinak’ – the clone colony.
The point to keep in mind is that children are not just ‘averages’ of the genetic input of the parents… they’re random recombinations. That can trigger sports - children who show traits that the parents do not have, (because the parents had repressed recessive genes that show in the children.)

Hope this helps.

I guess I was under the mistaken assumption that the sequence in a particular chromosome is , to borrow a term from math, “orientable”. So if we call the two sequences, seq 1 and seq 2, when recombining into a child, bits from seq 1 would wind up in child’s seq 1 and bits from seq 2 would wind up in child’s seq 2. I think it’s because DNA is always drawn as a helix and it would seem that bits from the “left” strand would wind up in the “left” strand and bits from the “right” strand would wind up in the “right” strand.

So, I guess this means that for any genetic bit from Bob, bob’s children with Jane would either have Bob’s arrangement, or a copy of itself. To calculate the probability of Bob’s and Jane’s child being identical to them we would have to know what’s the fundamental number of base pairs that gets copied at a time.

So,

a) What’s that fundamental number? Is it 1?

b) What would be a way (if any) to produce multiple copies of the same individual without cloning every single one? Do you think it’s possible to short circuit the reproductive system to produce non-haploid clone eggs?

Bad science abound.

Presuming we have Bob and Jane as you’ve described them (a huge presumption), Bob will have a complete set of genes, half of which he inherited from his mother, and half of which he inherited from his father. All of his genes put together are not on one strand, but 46 separate strands. 22 of these are very similar to another 22, but one set of them are from mom, one set from dad. These 44 chromosomes are each a long linear chain of double stranded DNA, which means they have a left half and a right half, and those two strands stay stuck together during all of the parts of this process you’re concerned with. Together, these 44 chromosomes are called Autosomes, which means they’re not the Sex chromosomes. Another one is called X, and he got it from mom. It doesn’t look or smell or taste anything like an X. It’s a linear chain of double stranded DNA. Another is called Y, which he got from pop. Again, it’s a linear strand of double sided DNA, which we’ve designated Y for convenience. These are called Sex Chromosomes. Forty-four plus two brings us up to the requisite 46 pieces of double stranded DNA.
Jane is similar, but her forty-sixth strand is a duplicate of Bob’s forty-fifth.

Now… When Bob and Jane get together and be incestuous, the relevant cells from Bob (called sperm) and the relevant cells from Jane (called ovum) combine into one. Remember that the one cell that’s combined has to have 46 chromosomes; two copies each of 22 autosomes (for 44), one X chromosome, and one chromosome that’s either an X or a Y, to determine the gender. The reason why this child isn’t another clone of Bob is this: the combination of which autosomes it got from Bob came from Bob’s mom and which came from Bob’s dad are completely random. Indeed, even portions of the same autosome can come from both grandma and grandpa. There’s a process called recombination or crossing over that occurs when sprem and ovum are formed that amounts to shuffling a deck.

So we now have an interactive example. Imagine, or acquire, two sets of 52 card poker decks. It’s better if you have the bicycle brand cards, a red and blue deck. Both decks contain the same cards, both have a King of Hearts and a Queen of Diamonds and so forth. Each deck represents a person. Bob is the blue deck, Jane is the Red. Shuffle each deck, and pull out the first two cards of each value you come across. Pull out the first two kings from the red deck, the first two queens, etc. Discard the remainder of the red deck, and do the same for the blue. Now combine the cards you pulled out and have a look at what you’ve got. You have a 52 card deck, which has the correct number of kings, queens, and on down the line. But the combination of suits which you have in your new deck (the baby) aren’t the Spade/Diamond/Club/Heart which Bob originally had and Jane copied. You’ve got potentially a 7 of hearts, two 7’s of diamonds, and a 7 of clubs. You have the right number of 7 cards, four of them to be precise. That’s the same number Bob started with. But it’s got a unique combination of those 7’s which doesn’t resemble what either Bob or Jane had. You also have no 7 of noses, or some other suit which you didn’t have to start with.

Nothing new was created when you divided your decks (simulating meiosis, or creation of sperm and eggs), but you wound up with something unique when you combined a sperm with an egg. Everything in your baby is clearly derived from Bob, but it’s not a clone of him.

It’s simply the wrong question.

The point is that we aren’t discussing base pairs here. We are discussing chromosomes. Chromosomes are discrete packets of genetic material millions of base pairs long. There is some small amount of what is termed “crossing over” where sequences of base pairs are exchanged the way you describe but it is absolutely trivial compared to chromosomal assortment.

For a child to be identical to Bob it would need to get exactly the same copies of each chromosome form Jane as Bob already has.

See if this analogy helps.

Imagine that the human genome is like a library with 46 book in it. Those book represent the different chromosomes. However although there are 46 books these are not 46 different books. They are in fact two different printings of 23 different books. So for example Bob/Jane will have a 1920 and a 1970 copy of “Moby Dick”. And a 1987 and 1990 copy “Grapes of Wrath”. And so on for all the books. Each book in the pair contains the same essential information, it tells the same story, but the pages are in slightly different orders, the forewords are different, some spelling may even have been changed. But they are essentially the same book. Thus it is with chromosomes. 23 basic chromosomes, each with two slightly different versions giving a total of 46 chromosomes per individual.

What happens in children is that they get one copy of version of book/chromosome form each parent. So to consider just “Moby Dick” a child may get Jane’s 1920 copy and Bob’s 1970 copy, or Bob’s 1920 copy and Jane’s 1970 copy. In that case they will be genetically identical to the parent of the same sex. But they can also get Bob’s 1970 copy and Jane’s 1970 copy and end up with 2 recent editions. They will be genetically different from either parent. Or they could get 1920 editions form both Joe and Jane and end up different. And so on for all the books/chromosomes. They might get Bob’s 1920 copy and Jane’s 1970 copy of Moby dick and be similar WRT that chromosome, but get two 1987 copies of “GOW” in which case they will be genetically dissimilar to their parents.

In contrast crossing over simply means swapping a couple of pages/genes between different versions. So you end up with an essentially 1970 version with a couple of 1920s pages. It’s a relatively trivial change to the library compared to the massive changes involved with the actual.
Now all that gets further complicated because Bob could already have two 1920 copies of a book. In that case so will Jane, and all children will need to get the identical chromosome pair 100% of the time. The more duplicate pairs Bob has the better then chance of the children being identical.

So basically to calculate the chances of Bob’s and Jane’s child being identical to them we would need to know the chance of a child getting exactly the same chromosomal configuration as him. There is roughly a 50% chance of this occurring for each of 23 chromosomes which, if my maths is correct, gives a 0.000011920928955078125% chance of any child being the same as either parent. Plan on having lots of kids before you get lucky.

You could do it by enuring the individual is chromosomally identical for each chromosome. That would require some fancy genetic engineering in its own right.

Yes, there was a discussion on this very topic a couple of weeks ago if you want to do a search on my name and parthenogenesis you should find it.

But why would you want to? It’s a convoluted way of producing a clone. Why not simply clone that diploid cells form the get go?

I’ll throw in a few thoughts here, mostly about the ‘double helix’

  • Technically, bits from the left strand are always the ‘inverse’ of those in the right strand. This is because the four possible DNA bases have different molecular ‘lengths’, but the distance between the strands of the helix will remain constant, so an A base will always get matched with a T on the other strand of the same helix, and C to G. (At least, I remember learning that it had something to do with molecular length. Wikipedia seems to imply that the reason for this is all about inter-base-pair bonds.)

  • This has nothing to do with what I was talking about in terms of ‘two different sequences.’ These are not on the same double helix, but seperate helices, read and interpreted the same way in the human genetic code, but containing variations.

  • Not sure what you mean about a ‘fundamental number of base pairs that get copied at a time’ or how that would help… apparently it’s somewhere on the order of 50 million to 200 million, depending – the different chromosomes have different numbers of base pairs on them. Umm… on second thought I think Blake has come close to answering the question you were trying to ask here.

I guess I was trying to calculate the number of different individual genetic makeups that you would find among Bob and Jane’s incestual descendants. If it’s chromosome level, then for each chromosome a descendant can have 3 combinations (say Bob/Jane have A and B chromosomes) : AA, BB, AB. Having 23 pairs, we get 23*3 = 69 different individuals. Right?

Try 3 to the 23rd power, 3^23, which is about 94 billion. Patterns with numerous ABs are more likely than the others, since there are two different ways to get an AB (A from mother, B from father, or the other way around,) But still… that’s a lot of different patterns. Even if you generously assume that there are only 15 chromosomes with significant differences on them, that leads to 14 million different patterns. Ain’t biology amazing??

(And, on a side note, it’s incredible how many of the findings from working out the theoretical details of human-alien hybrid genetics from ‘Roswell’ carries over to this clone stuff. :smiley: )

I’m not sure ‘incestuous’ fully captures the ickiness of this idea.

-rainy

More like disappointing. I’m very used to the idea of having an utterly large number of anything (stars, grains of sand, neurons, cells, atoms, possibilities, etc.) It’s the situation when things converge that intrigue me - that’s why I was so excited about the possibility of generations of clones.

Well, even things that are amazing aren’t guaranteed to work out the way you want them to. :wink: One way to think of it is that our biology isn’t set up in such a way to encourage stability, even (or especially) from a relatively heterogenous starting group. Sports, like mutants, are sometimes poor specimens who won’t survive long, but every so often they can totally kick ass. The fact that life, of any sort, tends to diversify is probably the reason that it’s survived on our planet for so long.