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Paul Andersen describes the major mutations found in the living world. He starts with an analogy comparing the information in DNA with the information in a recipe. Changes in the DNA can result in changes to the protein, like changes in the recipe can result in changes in the food. He describes the three major point mutations; substitutions, deletions and insertions. He also describes several chromosomal mutations.

Brief online animation, followed by 5 question quiz

[ February 17, 2008 ] People who lack a certain large segment of DNA have a previously unrecognized syndrome characterized by mental retardation, seizures, and slight physical abnormalities, according to a genetic analysis conducted by HHMI investigator Evan E. Eichler at the University of Washington School of Medicine and a team of international collaborators. The deleted DNA segment is responsible for just a small percentage of cases of mental retardation, but "when you think about how common mental retardation is," Eichler says, "this deletion has a significant impact on human health."

The Y chromosome is only one-third the size of the X. Although the Y has a partner in X, only the tips of these chromosomes are able to recombine. Thus, most of the Y chromosome is inherited from father to son in a pattern resembling asexual, not sexual, reproduction. No recombination means no reassortment, so deleterious mutations have no opportunity to be independently selected against. The Y chromosome therefore tends to accumulate changes and deletions faster than the X. Degradation doesn't occur in X chromosomes because during female meiosis, the X has the other X as a full partner in recombination.