Even so, genome size and the number of genes present in an organism reveal little about that organism's complexity — Nature.com
I don't have time to go into detail on Genetic Science, so I'll just mention that in Systems Theory, Reductive complexity (sheer numbers) is distinguished from Holistic Complexity (interrelationships). Reductively & numerically, a pile of sand may be "complex" (thousands of grains), but add a cement binder (links between grains), and the resulting concrete is a holistic system that is much stronger, and more complex, than its component parts.and taking into account that increasing complexity in organisms generally means complexity in phenotype, it should be the case that more complex the organism, the greater its genome size. — TheMadFool
Seems to me that you answered your own question in your OP. The phenotype is determined by not just the genotype, but by the environment as well. Think of phenotype as a feedback loop between genotype and the environment.Does Genotype Truly Determine Phenotype?
Genotype = The genetic composition of organisms
Phenotype = The set of observable characteristics of an individual [[b]resulting from the interaction of its genotype with the environment.[/b]] — TheMadFool
Right, the grains and the medium binding the grains is a more complex system than just grains. We can't talk about things without talking about how those things interact with other things or are determined by other things, like the environment it is part of. It's not that it is more complex, it is that it impossible that objects can be apart and not determined by the very environment it is part of, and all objects are parts of environments.I don't have time to go into detail on Genetic Science, so I'll just mention that in Systems Theory, Reductive complexity (sheer numbers) is distinguished from Holistic Complexity (interrelationships). Reductively & numerically, a pile of sand may be "complex" (thousands of grains), but add a cement binder (links between grains), and the resulting concrete is a holistic system that is much stronger, and more complex, than its component parts. — Gnomon
Considering the scientific consensus that genotype determines phenotype and taking into account that increasing complexity in organisms generally means complexity in phenotype, it should be the case that more complex the organism, the greater its genome size. — TheMadFool
I've answered the OP with demonstrable scientific facts, so I'm not sure what there is left to debate and why you still find it hard to believe. To reiterate once again simply:
1. There is not a one-to-one correspondence between genes and phenotypal complexity: e.g. the layout of blood vessels in the body is extremely complex, and it isn't coded directly in the genes.
2. Most DNA does not code for anything, or redundantly codes for the same protein. This is why there is no simple correlation between size of genome and complexity of the organism. Often the primary factor in how big a genome is is how many chromosome duplication events have occurred in an organism's history. — Mijin
You should probably consult the field of epigenetics.
Genes may or may be expressed depending on environmental and other influences.
So genes are not destiny. There is an interplay between your genetic code and the environmental experience which determines phenotypes and gene expression and interplay.
Your genetic clone would not be you, having had a lifetime of different experiences and influences. — prothero
Given what I said in the preceding paragraph and it's true that genotype determines phenotype, it must be that more complex organism should possess larger genomes and more genes. — TheMadFool
What do you think of the clip? — TheMadFool
The three-letter nature of codons means that the four nucleotides found in mRNA — A, U, G, and C — can produce a total of 64 different combinations. Of these 64 codons, 61 represent amino acids, and the remaining three represent stop signals, which trigger the end of protein synthesis.
Because there are only 20 different amino acids but 64 possible codons, most amino acids are indicated by more than one codon. This phenomenon is known as redundancy or degeneracy, and it is important to the genetic code because it minimizes the harmful effects that incorrectly placed nucleotides can have on protein synthesis.
https://www.nature.com/scitable/topicpage/the-information-in-dna-determines-cellular-function-6523228/
I'm trying to find some way for a smaller genome to pack more punch than a larger one. — TheMadFool
Assuming a one-to-one correspondence between genes and proteins would mean that there are at least 20,000 proteins corresponding to roughly 20,000 genes for humans. The proteome can be larger than the genome, especially in eukaryotes, as more than one protein can be produced from one gene due to alternative splicing (e.g. human proteome consists 92,179 proteins[citation needed] out of which 71,173 are splicing variants[citation needed]).
On the other hand, not all genes are translated to proteins, and many known genes encode only RNA which is the final functional product. Moreover, complete proteome size varies depending on the kingdom of life. For instance, eukaryotes, bacteria, archaea and viruses have on average 15,145, 3,200, 2,358 and 42 proteins respectively encoded in their genomes.
https://en.wikipedia.org/wiki/Proteome
Yes, I've been trying to get my hands on a good definition of "complexity" with no success. — TheMadFool
The proteome can be larger than the genome, especially in eukaryotes, as more than one protein can be produced from one gene due to alternative splicing
Algorithmic complexity is another more mathematical way of framing the issue - the search for the most compact program that could generate some particular bit string. — apokrisis
That means there's no clear-cut definition of genes and ergo, genomes. Biology, unlike physics, appears to be more fluid. Perhaps the issue will be resolved once we define "gene" and "genome" in a better way. — TheMadFool
Yes, I was thinking along those lines, wondering whether multifunctional swiss knives qualify as an instance of complexity. — TheMadFool
One problem though: it's generally believed that evolution evinces a progress from simplicity to complexity... — TheMadFool
but if you take the idea of algorithmic complexity and apply it to the universe then, since the universe began, according to a science book, by fixing the value of just six numbers (referring to known physical constants), doesn't that mean the graph of complexity is showing a downward trend? After all there are more bits of information in our genome than in there are in just six numbers? — TheMadFool
1. I'm intrigued by the fact that no two vascular trees are identical. However is a vascular tree an instance of complexity? Granted that, as I said, no two are identical but a bird's eye view of the vascular system bespeaks a simplicity - a result of a simple random branching algorithm. Nothing that's beyond the capacity of genomes. — TheMadFool
As you said, there's some parts of our genome that don't code for any protein and are labeled as junk DNA but this is, as is the case in all of science, only the current best judgement on the matter. — TheMadFool
If it turns out that junk DNA truly has zero phenotype information content then it speaks in my favor - genotype is not sufficient to explain phenotypic complexity. — TheMadFool
the genome is a recipe for how to make a human. It doesn't, and couldn't, encode everything about the end product. — Mijin
"Best judgement" is somewhat misleading here, making it sound like some best guess. — Mijin
So we can be very confident at this point that junk DNA is a thing — Mijin
As with all of science, we could be wrong. — Mijin
I don't follow your logic. — Mijin
this point was addressing your point about how simpler organisms can have a bigger genome than humans. Well, this is the answer. — Mijin
There is just nothing in the physics that explains what is going on anymore — apokrisis
I found an interesting theory - https://www.sciencedirect.com/science/article/pii/S1674205215001604
A likely reason for all the junk DNA is that DNA would become parasitic on itself. Individual segments would start copying and pasting themselves into the genome if they can get away with it. That would be just selection at work. The genome would become host to its own parasitic segments and so become bloated.
Then to explain why this happens to some genomes and not others, this paper argues that the genome has a delicate epigenetic network whose balance would be disturbed by this junk DNA inserting itself randomly. Mostly such defects would get edited out by evolution if the fitness of the genome was thus compromised.
But if a bit of parasitic DNA spawned a shower of copies, and these got inserted in a way that kept the global epigenetic network in balance, then the genome would still be fit and sudden bloating by multiple segments would be invisible to the forces of selection. The genome would be stuck with this parasitic load.
So it is a neat suggestion. The paper has a lot of good general background too.
Another relevant article is - https://www.scientificamerican.com/article/is-junk-dna-what-makes-humans-unique/
This talks about how the difference between ape and human brains is more about the epigenetic timing of cell division and growth schedules than the expression of any particles coded proteins. — apokrisis
but DNA replication is supposed to be high precision machinery - like the best of atomic clocks - and any malfunction should manifest itself in catastrophic failure in an organism — TheMadFool
My personal view is that junk DNA, although not carrying information for proteins, serve a purpose... — TheMadFool
I think a lot of people assume that DNA evolved - but how could natural selection apply before inheritance, and how could inheritance exist before something to code it? — Wayfarer
Get involved in philosophical discussions about knowledge, truth, language, consciousness, science, politics, religion, logic and mathematics, art, history, and lots more. No ads, no clutter, and very little agreement — just fascinating conversations.