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10.2: Origins of Molecular Polymorphisms

Mutations of DNA sequences can arise in many ways (Chapter 4).  Some of these changes occur during DNA replication processes, resulting in an insertion, deletion, or substitution of one or a few nucleotides.  Larger mutations can be caused by mobile genetic elements such as transposons, which are inserted more or less randomly into chromosomal DNA, sometimes occurring in clusters.  In these and other types of repetitive DNA sequences, the number of repeated units is highly prone to change through unequal crossovers and other replication events.