- #1
fluidistic
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Hello, I am reading the Selfish gene by Richard Dawkins. I am confused on genes. In some part of the book he gives us clues on how to compute the percentage of genes we have in common with relatives, such as parents and brothers and sisters, in those particular cases it is stated that we share 50% of our genes with them, i.e. about half our genes are to be found in any brother/sister/parent. Great, it kind of makes sense.
Mentally, if I zoom into almost any cell (i.e. excluding gametes and cells lacking nucleus) in an organism and I focus on the nucleus (if there is any), then I should see the different chromosomes that contain the DNA (as well as the "junk DNA"), i.e. the "code" to build that organism. The DNA is just an assembly of four proteins, i.e. large molecules. What differs, at that level, between an onion and a human is the sequence of those 4 proteins. Most of the DNA is not useful information, roughly 2% of it really contains the information necessary to build the body. This information is separated by chunks of apparent useless protein molecules (ACDG). Ok great. Now, a gene would be a sequence of ACDG proteins that is not cut during meiosis and so can be passed on future generations. So natural selection can act on those genes. A "bad" gene would be a gene that is less successful in making an individual able to pass on its genes. But it is not so easy to tag a gene as bad or good, not only because most of the genes are affected by other genes (so a seemingly bad gene can turn out to be a good gene if there is another gene present in a particular individual but not in other), but because it is also dependent on the environment of the individual. Etc.
It is also stated that if we take two non relative individuals in a population, it is safe to assume that they share no gene, their relatedness is 0%. I can imagine this to be true in a species that has had enough time to have hundred of thousands if not millions of generations, and a non negligible rate of mutations, but ok, let's assume this to be true for humans. Then why is it stated on the Internet, that we share about 40% of our genes with a banana for example? If this were true, then we should care more about the future of a banana than the future of our cousins, or grandparents / grandsons/granddaughters. Because, by ensuring the banana is successful in passing its genes, we also ensure a good part of our own genes are passed into the next generation. And thus more of our genes are passed to the next generations than if we had saved, for example, our grandson. This doesn't seem intuitively correct to me. What am I missing?
Mentally, if I zoom into almost any cell (i.e. excluding gametes and cells lacking nucleus) in an organism and I focus on the nucleus (if there is any), then I should see the different chromosomes that contain the DNA (as well as the "junk DNA"), i.e. the "code" to build that organism. The DNA is just an assembly of four proteins, i.e. large molecules. What differs, at that level, between an onion and a human is the sequence of those 4 proteins. Most of the DNA is not useful information, roughly 2% of it really contains the information necessary to build the body. This information is separated by chunks of apparent useless protein molecules (ACDG). Ok great. Now, a gene would be a sequence of ACDG proteins that is not cut during meiosis and so can be passed on future generations. So natural selection can act on those genes. A "bad" gene would be a gene that is less successful in making an individual able to pass on its genes. But it is not so easy to tag a gene as bad or good, not only because most of the genes are affected by other genes (so a seemingly bad gene can turn out to be a good gene if there is another gene present in a particular individual but not in other), but because it is also dependent on the environment of the individual. Etc.
It is also stated that if we take two non relative individuals in a population, it is safe to assume that they share no gene, their relatedness is 0%. I can imagine this to be true in a species that has had enough time to have hundred of thousands if not millions of generations, and a non negligible rate of mutations, but ok, let's assume this to be true for humans. Then why is it stated on the Internet, that we share about 40% of our genes with a banana for example? If this were true, then we should care more about the future of a banana than the future of our cousins, or grandparents / grandsons/granddaughters. Because, by ensuring the banana is successful in passing its genes, we also ensure a good part of our own genes are passed into the next generation. And thus more of our genes are passed to the next generations than if we had saved, for example, our grandson. This doesn't seem intuitively correct to me. What am I missing?