Changes

==Beneficial mutations==

==Beneficial mutations==

A very small percentage of all mutations actually have a positive effect. These mutations lead to new versions of proteins that help an organism and its future generations better adapt to changes in their environment. For example, a specific 32 base pair deletion in human CCR5 (CCR5-32) confers [[HIV]] resistance to [[Zygosity|homozygotes]] and delays [[AIDS]] onset in [[Zygosity|heterozygotes]].<ref>[http://www.cdc.gov/genomics/hugenet/factsheets/FS_CCR5.htm]</ref> The CCR5 mutation is more common in those of European descent. One theory for the [[etiology]] of the relatively high frequency of CCR5-32 in the European population is that is conferred resistance to the [[bubonic plague]] in mid-14th century Europe.<ref>[http://www.pbs.org/wnet/secrets/case_plague/clues.html]</ref>

A very small percentage of all mutations actually have a positive effect. These mutations lead to new versions of proteins that help an organism and its future generations better adapt to changes in their environment. For example, a specific 32 base pair deletion in human CCR5 (CCR5-32) confers [[HIV]] resistance to [[Zygosity|homozygotes]] and delays [[AIDS]] onset in [[Zygosity|heterozygotes]].<ref>[http://www.cdc.gov/genomics/hugenet/factsheets/FS_CCR5.htm]</ref> The CCR5 mutation is more common in those of European descent. One theory for the [[etiology]] of the relatively high frequency of CCR5-32 in the European population is that it conferred resistance to the [[bubonic plague]] in mid-14th century Europe.<ref>[http://www.pbs.org/wnet/secrets/case_plague/clues.html]</ref>

==References==

==References==