10 Units of selection - BIO 370 Kirkpatrick Hall Fall 2004 p 1 10 Units of selection Natural selection can cause evolution in any population that meets

10 Units of selection - BIO 370 Kirkpatrick Hall Fall 2004...

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BIO 370 Kirkpatrick & Hall, Fall 2004 p. 1 10. Units of selection Natural selection can cause evolution in any population that meets the conditions of our “Theorem of evolution by natural selection” The population can consist of molecules, organelles, individuals, groups, .... Selection on the level of molecules Repetitive DNA Extra copies are sometimes made off short sequences of noncoding DNA when the chromosome is replicated This “repetitive DNA” can accumulate in large numbers of copies Example: The ALU sequence in humans makes up about 5% of the human genome. It has no know function, but seems to have accumulated simply because extra copies are made accidently during DNA replication Transposons These genetic elements are capable of actively copying themselves They code for an enzyme that allows them to make duplicates that insert themselves elsewhere in the genome They act much like viruses, but never leave the nucleus Transposons in Drosophila make up 10% of the genome Transposons are typically bad for the individual that carries them When they insert into the DNA, transposons can disrupt the function of critical genes Selection at the level of organelles Organelles (mitochondria and chloroplasts) have their own genomes The different mitochondria within a cell can compete with each other Mitochondria in yeast have mutations that delete a large piece of their genome This allows the mitochondrion to replicate itself faster Daughter yeast cells will then carry more copies of the mutant mitochondria But if all the mitochondria in the yeast cell carry the mutation, the cell dies because it cannot carry out some critical metabolic functions

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