stevevw wrote:
Kenisaw wrote:
There's no such thing as mutations = loss of information. That is creationist pseudoscience. And here's a simple way to know that: reversions. A reversion is a reversed mutation, and it is a common event. A DNA base goes from an A to a G, and then back to an A again. According to creationists, the switch from an A to a G is a "loss of information". When the G switched back to an A, they would also call that a "loss of information", since they claim ALL mutations create information loss. Clearly that is moronic.
Yeah, the concept of information is hard to pin down when it comes to evolution. It's not just about Shannon information but also about biological function. I am not a creationist so I don't know what they consider info is. Even so, the example you give is really talking about the changing of existing genetic info. Normally if a cell is damaged by a mutation it is harder for it to repair that so it ends up cutting off that function to survive otherwise it will take too much energy to deal with and become a cost to fitness. It's harder for a cell to produce multi-mutations to repair that damage than to produce a single mutation that will disengage that part of the cell.
I don't believe this is biologically accurate. If a cell is "damaged" by a mutation it may not function properly, and basically sit there until it is replaced, or make copies of itself and make lots of cells that don't function properly (cancer can happen in such a scenario). Since no function in your body relies on just one cell, the body does not end up "cutting off that function to survive". If a liver cell didn't work right, would the entire liver be stopped? No.
And cells don't produce "mutations" to repair damage. If a mutation is not caught when the cell is being produced, the cell just has that mutation going forward. It doesn't know it is different from the other cells. If it starts behaving in a way that is dangerous to the body, the immune system might attack and destroy it. If the cell isn't doing anything overtly bad, it just exists until replacement time and passes the mutation on to the next cell.
Regardless of all that, if a mutation doesn't happen in a germ cell (sperm or egg) than it doesn't get passed on anyway. That liver cell I mentioned? You can't pass that on to your kids...
What I was referring to with antibiotic resistance was how bacteria loses some function to become resistant to antibiotics because mutations harm the ribosome of the bacteria so that antibiotics were not able to attach. The bacteria population has lost the ability to produce individuals that are sensitive to antibiotics. No new genetic information or function was produced rather it was lost and cannot be put back.
Again, I just specifically explained reversions and how you've ended up with the exact same DNA as a result of two mutations. It just so happened that the second mutation reversed the first. If I have a mutation, and then a second one reverses it, and that happens 18 billion times, I'm still left with the exact same DNA that I started with 18 billion mutations ago. According to you that means I've had a huge loss of "information or function". See how silly that notion is?
Ribosomes are not harmed, or improved, by mutations. They are merely changed. It is the organism's ability to survive and thrive in it's environment that may be harmed or improved. The bacteria you mention may have lost "sensitivity" to a certain antibiotic, but it gained survivability. It basically changed how it reacted to a certain molecule (or group of molecules). This isn't information, it's chemistry. If that antibiotic stopped being used, we know from reversions that it could gain that "sensitivity" again in the future.
DNA is not a code. Yes, I know people always say it is like a code, but they use that as a metaphor to help people understand what they are talking about. DNA is just a really complex molecule that is used as a template to make other molecules. When DNA changes, the amount of certain proteins or other molecules that it makes is increased or decreased or sped up or slowed down. There is no genetic standing for the claim that mutations are a loss of information. They aren't. They are simply a change to the DNA molecule.
Maybe so but there sure is a lot of articles out there saying that DNA is a code or language or an operating system.
Millions of DNA switches that power human genome's operating system are discovered
https://www.sciencedaily.com/releases/2 ... _TrendMD_0
Scientists Discover A Genetic Code For Organising DNA Within The Nucleus
https://www.sciencedaily.com/releases/2 ... 103909.htm
Scientists Discover Parallel Codes In Genes
https://www.sciencedaily.com/releases/2 ... 230116.htm
Like I said, it's a metaphor. Think of it this way - there are 7 billion humans on this planet, and each one has their own unique set of DNA. What code do you know of that can have 7 billion variations of it and it still works the same? What language can have 7 billion variations to it and still be functional? DNA is not information and it is not a code. It's a big molecule (made up of just 4 basic parts by the way) that acts as a template for making other molecules, and those other molecules make us look and do what we are. We are self replicating carbon units, nothing more...
Stevevw said
It's a bit like antibiotic resistance in bacteria. Although the mutant bacteria can survive in the environment where it has become resistant to antibiotics, the change has come at a cost. The altered protein is less efficient in performing its normal function, making the bacteria less fit in an environment without antibiotics. The non-mutant bacteria are better able to compete for resources and reproduce faster than the mutant form.
That's silly. Antibiotic resistant bacteria still live and spread in humans just as easily, but they aren't killed as easily, which means they are more successful at reproducing. If that isn't a benefit to the bacteria, I don't know what is...
It may be a benefit for resisting antibiotics but that benefit came for the switching off or loss of an existing function, nothing new was added.
Bacterial Adaptation through Loss of Function
The metabolic capabilities and regulatory networks of bacteria have been optimised by evolution in response to selective pressures present in each species' native ecological niche. In a new environment, however, the same bacteria may grow poorly due to regulatory constraints or biochemical deficiencies.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3708842/
Did you read this article yourself, or just post it up because of the title and the beginning of the abstract? I ask because it seems pretty obvious to me that you think this study means that all beneficial mutations are a result of genes switching off or deletions in the genome. As the paper states: "While rare mutations that modulate specific network connections can engender the appropriate regulatory capacity (for example, the hijacking of an aerobic promoter to enable aerobic citrate metabolism in Escherichia coli during a long term evolution experiment [8]), comparatively common loss-of-function (null) mutations [9] that produce less specific perturbations could also generate advantageous network adjustments." In other words, increase in fitness can happen either way. Your assertion that it takes "loss of information" to increase survivability is patently false. The E coli citrate example mentioned above found additional genes added to the genome allowed the bacteria to use citrate as a food source.
The paper also mentions: "The relative abundance of null mutations coupled with their adaptive potential suggests that specific null mutations likely represent common early steps in the evolution of bacterial populations encountering a new environment." In other words, a null mutation is not necessarily the only mutation that a population will undergo in order to survive a new environment, but it might be type of mutation that allows it to at least survive the initial change in environment.
In fact you should read the whole introduction portion of the paper, they do a pretty good job of discussing null allele activity as being one type (not THE type) of evolutionary pathway during significant environmental change. (Please note by the way that these null alleles are much more likely to succeed when significant environmental changes occur. That was the point of the paper and the experiment itself - make drastic changes to things like food source and see how the bacteria react to survive).
Stevevw said
I would have though the beneficial mutation frequency was important as there need to be many to account for all of life. If they are very very rare and deleterious mutations are more common then there must have been a multitude of harmful mutations.
Depends of many factors, wouldn't you say? After extinction events, when a lot of niches are opened up in the environment, a lot more mutations would be considered useful since there is more opportunity for that new ability to survive. Some mutations involve hundreds of DNA pairs at a time, which can affect a larger change in one fell swoop. When the magnetic field flips, there is often a reduced strength in the magnetic field which allows for more mutations to happen during that time frame due to increased radiation. There really is no reason to think that mutations rates, beneficial or otherwise, happen at a consistent pace...
Maybe so, but you also have to consider that changes may be the results of other non-adaptive processes besides evolution by natural selection and random mutations. So we have to determine this before we start attributing everything to adaptations. Life may have the ability to tap into vast amounts of genetic info or change through processes such as developmental bias, genetic recombination, gene transference mechanisms, natural genetic engineering, plasticity, niche construction, extra-genetic inheritance etc. So life may use pre-existing genetic info or may have more ability to change without an evolutionary process.
Some of those things ARE evolutionary processes, Steve. It is thought that bacteria in particular experience gene swapping and insertion changes to their genome, because all it takes is getting through one cell wall and getting mixed in with the existing DNA for that particular species. Much easier than that happening to eukaryote like you and me. Others, like natural genetic engineering, have been latched onto by creationists even though the hypothesis founder (Jim Shapiro) has repeatedly refuted the attempt to hijack the concept by ID proponents.
Evolution is simply the change in inheritable characteristics of a population of animals over time. If a niche constructor (like a beaver) evolves to better fit the water environment they have created, that is still evolution. Beaver's cannot control what evolutional changes they receive to their genome, so there is no guarantee that they will become better suited to their created biome.
Does evolutionary theory need a rethink?
Missing pieces include how physical development influences the generation of variation (developmental bias); how the environment directly shapes organisms’ traits (plasticity); how organisms modify environments (niche construction); and how organisms transmit more than genes across generations (extra-genetic inheritance). For SET, these phenomena are just outcomes of evolution. For the EES, they are also causes.
http://www.nature.com/news/does-evoluti ... nk-1.16080
Natural genetic engineering in evolution.
https://www.ncbi.nlm.nih.gov/pubmed/1334920
It's all evolution though. You are tapping into the discussions about how evolution occurs, not IF evolution occurs.
