21:9 - or decrease (they change in one direction) depending...

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21/9 NATURAL SELECTION Natural selection provides directional change in allele frequency relative to specific environmental factors. In the environment changes selection pressures also change If there are long term environmental changes in a consistent direction then allele frequencies should also shift gradually Directional change In a genetic sense the nonrandom change in allele frequencies caused by natural selection The change is directional because the frequencies of alleles consistently increase
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Unformatted text preview: or decrease (they change in one direction) depending on environmental circumstances and the selective pressures involved. Sickle-Cell anemia • A severe inherited hemoglobin disorder in which red blood cells collapse when deprived of oxygen. • It results from inheriting two copies of a mutant allele. • This mutation is caused by a single base substitution in the DNA....
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This note was uploaded on 02/07/2012 for the course DRAMA 100 taught by Professor Gihan during the Spring '11 term at Miramar College.

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