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Understanding Evolution

Understanding Evolution

Your one-stop source for information on evolution

Understanding Evolution

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      • 1_historyoflife_menu_iconThe history of life: looking at the patterns – Change over time and shared ancestors
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Home → Taking advantage of mutation

    Taking advantage of mutation

    Directed evolution can identify the useful molecules in a sea of useless ones, and select only the useful molecules for replication. However, the process can also fine-tune those molecules by incorporating a surprising tool: mutation.

    Illustration of original DNA sequence on the left and a copy of the sequence with a mutation on the right.

    A mutation is simply a change in the sequence of a DNA molecule, but mutations have a reputation for being harmful — for causing cancer, birth defects, and the like. How does the process of mutation help evolutionary engineers evolve useful molecules? The key is that although random mutations usually lead to either no effect or a detrimental one, selection can single out and preserve the occasional mutation that improves the function of the original molecule. It works like this:

    1. Initial population: Begin with a pool of RNA that does a particular job, such as binding to a toxin. The molecules are very similar to one another and bind the toxin equally well. This population has low genetic variation.

    Illustration showing a population of RNA with low genetic variation.

    2. Mutation: Produce a mutated pool of RNAs. This increases the genetic variation of the RNA pool. Most of the mutated RNAs don’t bind the toxin as well as they originally did — however, a few just happened to have sustained a mutation that improved their function.

    Illustration showing a mutated pool of RNAs.

    3. Selection: Test the pool of RNAs for ability to bind the toxin, and select only those that perform the best. This selected pool of RNA performs better, on average, than the original pool.

    Illustration of population of RNA with most crossed out and two that bind best to the toxin selected.

    4. Reproduction: Copy the selected RNAs.

    Illustration of best preforming RNA reproducing.

    5. Repetition: Repeat the process of mutation, selection, and reproduction. With each repetition, the pool of RNAs evolves and binds the toxin a little better.

    Illustration showing the steps of mutation, selection, and reproduction and then repetition. The end result being that with each repetition, the pool of RNAs evolves and binds the toxin a little better.

    In this way, selection (in this case, artificial selection) can transform the process of random mutation into one that leads to evolution in a particular direction.

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