BIOL359 Chapter Notes - Chapter 5: Reverse Transcriptase, Gene Duplication, Prophase

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New alleles arise from alterations to existing alleles. Mutations to new alleles can influence phenotypes if they alter the expression and/or function of proteins. The ultimate source of genetic variation is changes in nucleotide sequences, or mutations. Mutations can be as small as the substitution of one nucleotide for another. They can involve insertions or deletions of short or long runs of bases. They can entail the duplication of entire genes, making possible the evolution of new functions. Or they can be as large as rearrangements of chromosomes or doubling of the genome. Two mechanisms of gene duplication are thought to be among the most common sources of new genes. The first is unequal crossing over, an error in the genetic recombination that happens during meiosis. In normal crossing over, homologous chromosomes align side by side during prophase of meiosis i. In unequal crossing over, the homologous chromosomes align incorrectly. The second mechanism is called retroposition or retroduplication.

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