A question about DNA combinations Watch

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dh00001
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it would be yes but things would alter do to social and environmental conditioning.
plus during mitosis some errors occur so there would be differences on such a tiny scale. but yes its possible :hmmmm:
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Psyk
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I think the number of combinations would be so high it would probably take thousands of times longer than the universe has existed for there to be a realistic chance of there being two people who just happen to have the same DNA.
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8EnglishRoses
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My teacher is convinced that this is the case already. He thinks there is an even smaller amount of DNA combinations than current scientists believe, that as many as 2 in 600 000 people could be genetically identical. But that's just him....so, in short, yes.
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WhatTheFunk
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the way DNA is formed is to put so random, you get mutations in the DNA of a cell, when that divids that will then pass it on good or bad, cross over of DNA, random which chromosome gets pulled to the different sides of the cell, and many more
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Psyk
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(Original post by Durandal)
I know it's highly unlikely, but just knowing it could be possible fascinates me...
According to quantum physics pretty much anything is technically possible, like walking through a solid wall. It's just that the chance is so small, it might as well be impossible. Things like that will probably never happen in the entire lifetime of the universe.
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**mentalheroin**
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Thered hve to be alot of people. way, way more than there are now. and if there was that many people, say in 10000 years time, DNA would have even more possible sequences through evolution. And if two were created, there would be competition and one of them would surely die of murder
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WhatTheFunk
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evolution into two different form of human be more likely then running out od DNA combinations
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louisedotcom
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I wonder if there's anyone who looks like me out there

Everyone else I know seems to resemble someone else- even if its only slightly, but ive never seen anyone who looks even a little like me.
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Eubacterium
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(Original post by Durandal)
Before I ask, I'm not exactly well-versed in the field of genetics, so excuse me if I come across as ignorant, but this question has been bugging me for a while and I want to know the answer.

Now, assuming there is a finite amount of possible DNA combinations for humans, what happens when our population (excluding twins and clones) exceeds this number? Will there be people born who are unrelated and yet genetically identical to each other?

I probably worded that question badly, so I'll present it using a hypothetical scenario. Let's say for simplicity's sake, that there are 100 possible DNA sequences for human beings. Now, let's say we have a planet with a population of 100 humans, with no twins or clones ever being born. Now, logically speaking, the 101st child born on this planet should have genes identical to another member of the population. Could this ever happen? Or am I just unaware of another factor that would render such a scenario impossible?
Genes are constantly being mutated all the time. Not just in gametes (which are sperm and eggs but in normal cells also (which can lead to cancer). If it happens in the gametes it can be passed down to the next generation. Most mutations are lethal but some are advantageous and so become selected. Others may have little or no effect so just stay in the population. So that adds to genetic diversity. Also while the gametes are being produced there is genetic recombination (where the chromosomes of both parents line up in the middle of a dividing cell. Whether a paternal or a maternal chromosome goes into a daughter cell is random, leading to each resulting gamete containing a mixture of maternal and paternal chromosomes). Also each chromosome from one parent exchanges genetic information with its counterpart from the other parent (the chromosomes actually swaps parts). So the resulting chromosomes are a mixture of the maternal and paternal ones. So it is not possible for someone to end up genetically the same as a relation without cloning or being twins.
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WhatTheFunk
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(Original post by Eubacterium)
Genes are constantly being mutated all the time. Not just in gametes (which are sperm and eggs but in normal cells also (which can lead to cancer). If it happens in the gametes it can be passed down to the next generation. Most mutations are lethal but some are advantageous and so become selected. Others may have little or no effect so just stay in the population. So that adds to genetic diversity. Also while the gametes are being produced there is genetic recombination (where the chromosomes of both parents line up in the middle of a dividing cell. Whether a paternal or a maternal chromosome goes into a daughter cell is random, leading to each resulting gamete containing a mixture of maternal and paternal chromosomes). Also each chromosome from one parent exchanges genetic information with its counterpart from the other parent (the chromosomes actually swaps parts). So the resulting chromosomes are a mixture of the maternal and paternal ones. So it is not possible for someone to end up genetically the same as a relation without cloning or being twins.
thats what i was trying to say :p:
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Psyk
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(Original post by Eubacterium)
So it is not possible for someone to end up genetic the same as a relation without cloning or being twins.
I think the OP was getting at was could it happen purely by chance? I don't know much about genetics, but it's an example that comes up quite a bit in computer science lectures so I know a few basics. From what I understand DNA is made up of huge sequences of only 4 basic building blocks. Theoretically there is a chance that two people could have the exact same sequence. But I imagine the chances are so small it will never happen.
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Eubacterium
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(Original post by Psyk)
I think the OP was getting at was could it happen purely by chance? I don't know much about genetics, but it's an example that comes up quite a bit in computer science lectures so I know a few basics. From what I understand DNA is made up of huge sequences of only 4 basic building blocks. Theoretically there is a chance that two people could have the exact same sequence. But I imagine the chances are so small it will never happen.
It would be impossible as it would depend on largely on the genetics of the parents. So the parents of both the unrelated genetically identical people would also have to share the same genetics as each other. So would their parents, and their parents’ parents. Also only half of each genome is passed onto the offspring. so the both people would have to inherit the same halves. Then there could not be any of the genetic and chromosome alterations and assortment I mentioned. The only way that could happen sort of is if there were a lot of inbreeding (which would lead to lethal genes being expressed). Those building blocks are based on the genetic transcripts of the parents. They don’t build up randomly. There are mistakes but enzymes work to correct these as much as possible (and are very good at their job).
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Psyk
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(Original post by Eubacterium)
It would be impossible as it would depend on largely on the genetics of the parents. So the parents of both the unrelated genetically identical people would also have to share the same genetics as each other. So would their parents, and their parents’ parents. Also only half of each genome is passed onto the offspring. so the both people would have to inherit the same halves. Then there could not be any of the genetic and chromosome alterations and assortment I mentioned. The only way that could happen sort of is if there were a lot of inbreeding (which would lead to lethal genes being expressed). Those building blocks are based on the genetic transcripts of the parents. They don’t build up randomly. There are mistakes but enzymes work to correct these as much as possible (and are very good at their job).
But there is still a limited (although unimaginably large) number of possible combinations. What would happen if all those combinations had already happened?
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WhatTheFunk
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DNA come in all lenght, some protain that are form for DNA are thousand on tousand of bases long
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Eubacterium
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(Original post by Psyk)
But there is still a limited (although unimaginably large) number of possible combinations. What would happen if all those combinations had already happened?
Then there's a minute possibility of extraterrestrial life being human, having gone through the exact same evolution process we have and living in habits such as cities very similar to our own (as there is evidence that the 4 bases that make the genome may be abundant in the universe). I think common sense says it won’t happen…
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Psyk
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(Original post by Eubacterium)
Then there's a minute possibility of extraterrestrial life being human, having gone the exact same evolution process we have and living in habits such as cities very similar to our own (as there is evidence that the 4 bases that make the genome may be abundant in the universe). I think common sense says it won’t happen…
So basically we agree. Theoretically possible, but so hugely improbably it'll never happen.
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cabbage
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^^it sounds like it. Looking at the bigger picture if all the combinations had been used.
Its amazing to think that that is possible. (However unlikely) The concept is amazing.
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Robob
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Come to norfolk, only about 2 surnames here, not that many combinations of genes you can have.
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