DNA Required Life

Essential DNA Required for Life

ByĀ Philip Carlson

If one believes in evolution, it is important to know what is required for life. Not just what environmental conditions are needed, but also what biochemical conditions.

It is often quoted that there are 250 essential proteins required for basic life. To have life, you need 250 proteins so it was thought. While those were previous guesses it is now possible to determine what parts of DNA are essential for life. AĀ studyĀ released in the journalĀ Molecular Systems BiologyĀ provides a method of testing just that. Not only Ā do they give a method they also performed the test on a ā€œsimpleā€ bacterium (Caulobacter crescentus).Ā 

DNA Required Life

The complete genome of this bacterium was sequenced in 2001. Which helpsĀ tremendously with the task ofĀ determiningĀ which parts are essential for its survival. It is important to know that just because the genome was sequenced does not mean that the function of all the pieces is known, just that theĀ nucleobase sequence that makes up the DNA is known.

With the bacteria in hand, these researchers from the Stanford University School of Medicine took a close look at exactly what parts of DNA are required for this bacteria to live in the lab.

ā€œThis work addresses a fundamental question in biology: What is essential for life?ā€ saidĀ Beat Christen, PhD, one of the co-first authors of the new paper and a postdoctoral scholar in developmental biology. ā€œWe came up with a method to identify all the parts of the genome required for life.ā€(1)

What is essential for life from a biochemical standpoint? They came up with some interesting conclusions which dwarf the previous estimates.

In total, the essentialĀ CaulobacterĀ genome was 492,941 base pairs long and included 480 protein-coding genes that were clustered in two regions of the chromosome. The researchers also identified 402 essential promoter regions that increase or decrease the activity of those genes, and 130 segments of DNA that do not code for proteins but have other roles in modifying bacterial metabolism or reproduction. Of the individual DNA regions identified as essential, 91 were non-coding regions of unknown function and 49 were genes coding proteins whose function is unknown. (1)

We are told, ā€œthat 12 percent of the bacteriaā€™s genetic material is essential for survival under laboratory conditions.ā€ (1) Sounds like a small percentage overall, but keep in mind that thisĀ essentialĀ genome was 492,941 base pairs long. These are base pairs that are needed for life in this bacterium. This means that 985,882 amino acids were needed in the correct arrangement to allow life for this bacterium. The implications this has for the unaided formation of the first life are staggering. (While we could stop here and calculate theĀ apparentĀ overly absurd odds of this happening, such a calculation would serve little purpose. As a side note, creationist literature often attempts to calculate the absurd odds of things happening the way evolutions claim. Many set up straw men with these types of processes. I think that more often than not those types of calculations oversimplify the problems andĀ ashamedlyĀ make a caricature of theĀ opponentsĀ position. This type of ā€œargumentationā€ is best left off the table if any real headway is to be made with this issue. While I do believe that such odds could be calculated at a rudimentary level, it could never be done to complete satisfaction without knowing all the factors involved. We do know, however, that the improbability is greatly increased because of the sheer number of correctly sequenced amino acids needed.) The researches did find 480 protein coding regions that are essential. This nearly doubles the previous estimates of how many proteins are needed for life. While is is a bit of an extrapolation to say that all of those 480 proteins are needed for life I think we can say that if that part of the DNA is needed it stands to reason that so are those proteins. They also found 91 essential coding regions and 49 coding regions that have unknown function.

ā€œThere were many surprises in the analysis of the essential regions ofĀ Caulobacterā€™s genome,ā€ saidĀ Lucy Shapiro, PhD, the paperā€™s senior author. ā€œFor instance, we found 91 essential DNA segments where we have no idea what they do. These may provide clues to lead us to new and completely unknown bacterial functions.ā€ Shapiro is a professor of developmental biology and the director of theĀ Beckman Center for Molecular and Genetic MedicineĀ at Stanford. (1)

These 91 essential DNA segments that are of unknown function were still found to be essential to life! This reminds me of the oldĀ vestigialĀ organs argument often used in support of evolution. That is right, just because we donā€™t know the function does not means there isnā€™t one. See theĀ previousĀ discussion onĀ pseudogenesĀ for another example of that type of thinking.

This new research helps to contribute to our (mis)understanding of an evolutionary origin of life, and, I think, push us toward accepting that the transcendent creator did not use evolution to bring about life.

1.Ā Digitale, E. ā€œNew method reveals parts of bacterium genome essential to lifeā€. Stanford School of Medicine news release, August 30, 2011,Ā http://med.stanford.edu/ism/2011/august/shapiro.html

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16 replies
  1. Kyle says:

    Well this is a simple case of ignorance. No one who understands evolution and the origins of life to the extent science has provided believes evolution was the beginning. There is no evolution without life. Life had to exist before evolution could occur. What you are mistakenly referring to as evolution in this article is actually “abiogenesis”. This is the prevailing theory of how we went from not-life to life.

    I want to reiterate. Abiogenesis happens. This makes non-living become living. There is no evolution up until this point. Once there are living things, then evolution is able to shape life. These are two very distinct schools of thought. You cannot hope to slay the dragon of evolution by pointing out how it cannot support the beginning of life.

    Reply
    • Scott says:

      “Abiogenesis happens.”
      It certainly is a fancier name for spontaneous generation, but one can only say it happens – they can’t prove it whether is is 200 proteins or 480 proteins.

      ” Once there are living things, then evolution is able to shape life.”
      This I agree with, but not to the level of common descent. Give a single example where the number of genes of any living organism has increased.

      Reply
    • Brian says:

      Kyle, I think you’re correct in that the author is conflating two separate, yet related, issues – origins and evolution. However, after all the word smithing and finger-pointing, do you think the author is making a fair point regarding his interpretation of the study results – that life, even very primitive life, likely required much more information that previously theorized?

      Reply
      • Kyle says:

        He specifically addressed evolution, which was why my response was directed to that. As for his interpretation of the study results, what bearing does this have on anything? His intent was to use it to attack the theory of evolution. All it seemingly did for abiogenesis was raise the lower limit of required information. This isn’t a problem for abiogenesis.

        Reply
        • KR says:

          Kyle wrote: “All it seemingly did for abiogenesis was raise the lower limit of required information.”

          What it did was to establish the minimum set of genes required to maintain a C. crescentus cell. Why this would have any particular implications for the requirements of life in general is not clear to me – unless we’re now defining life as the propagation of C. crescentus cells, which doesn’t make much sense.

          Reply
  2. KR says:

    Scott wrote: “Give a single example where the number of genes of any living organism has increased.”

    This happens every time a gene gets duplicated through mutation. You know of at least one such example: Richard Lenski’s LTEE experiment, where an E. coli strain wenth through a duplication of a citrate transporter gene which allowed the E. coli cells to metabolize citrate in an aerobic environment.

    When there are two copies of a gene, negative selection may become more relaxed since a mutation will have less severe consequences. This means that one of the copies may diverge through further mutations and acquire a different function within the organism. Most proteins have such counterparts that have clear DNA homology but different functions. This is actually very strong supporting evidence of common descent as these patterns of divergence correlate with the patterns of relatedness derived from other genetic evidence like DNA synteny (the study of how genes are linked to each other on the chromosome), pseudogenes and endogenous retroviruses.

    New genes can also arise from mutations within previously non-functional DNA sequences (“junk DNA”) but this seems to be very rare.

    Reply
      • Brian says:

        I think this example is the best example, as it is the most common and does not require manipulation in a laboratory.

        On the other hand, as the general topic of this post is evolution, I don’t think this is a great example of human evolution do you?

        Reply
        • Kyle says:

          Why would it not be a great example of human evolution? Evolution does not dictate that mutations must be for the betterment of the species, only that it changes. Down Syndrome persists because it doesn’t negatively affect a person’s chance for survival anymore.

          Reply
        • toby says:

          There are also numerous trisomy mutations.

          On the other hand, as the general topic of this post is evolution, I donā€™t think this is a great example of human evolution do you?
          What would you consider a great example? I think you’re biased and are only looking for “positive” mutations. Down syndrome is an example of the genome expansion your ilk so desperately cries for, then you dismiss it because you see it a bad mutation. What you should be focusing on is that it’s exactly an example of what you ask for.

          Reply
  3. Ed Vaessen says:

    “If one believes in evolution, it is important to know what is required for life. Not just what environmental conditions are needed, but also what biochemical conditions.”

    Indeed: a most silly attack on evolution via the road of abiogenesis.
    It is as claiming that one can’t do sensible geology without knowing how elements like iron, silicon, oxygen and others are formed in stars or supernovae.

    This habit of asking questions about things that do not belong to the field of evolution has already lead to the claim that evolution cannot be true because it can’t explain the Big Bang.

    Reply
    • Andy Ryan says:

      Four biologists could have completely different ideas about how life began and yet could find no disagreement on evolution whatsoever. One could believe in God created life on earth, another could believe the planet was seeded by aliens, another could subscribe to abiogenesis, a fourth could throw up his hands and say he had no idea. And yet the four could collaborate on evolution research and find their differing beliefs have absolutely no effect whatsoever on their work together. And the scenario I give isn’t even a strange hypothetical ā€“ atheist and religious scientists collaborate all the time on research. If we found out proof tomorrow that life on earth was started by God, it wouldn’t affect the evidence of evolution in the slightest. I’m not even sure would affect our understanding of evolution.

      Reply
  4. Eugene Waldenmaier says:

    I approached this article trying to understand how the fist living cell came-about.
    Weather called “abiogenesis” (spontaneous generation) or random statistical luck … it’s easier (for me) to see an intelligent creator implementing a complex sequencing design (DNA forerunner) that could be deliberately manipulated (versus random failed mutations over time) to rapidly provide the millions of improved life forms and species that the designer desired. Sequential programming these DNA constituents could then give the archaeological appearance of a designer-less evolution.
    I readily support the premise of “micro-evolution”. But this would become touchy when a person then tries to defend the origin of a person’s soul.
    With all the computers, researchers and scientists … can any such group explain or improve-upon any single subsystems within a person. “Show me an improved eye”

    Reply
    • Andy Ryan says:

      Odd logic – if I can’t reproduce or improve on something in nature, that must mean that thing was intelligently designed. Why does that follow? Presumably if a scientist DID manage to improve on the human eye (and who’s to say certain cameras haven’t), a creationist could claim that shows one needs intelligent design.

      Reply
      • Ed Vaessen says:

        Indeed. It is the logical fallacy of shifting the goals posts.
        As long as science can’t improve on nature, it is a proof of God.
        As soon as science can, it is a proof of God too.

        Reply

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