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The Hardy-Weinberg Principle

The Hardy-Weinberg Principle. By: Alex, Jared, Merrick and Larisa. What Is It?. A principle that states in populations in which ONLY RANDOM CHANCE is at work, allele frequencies will remain constant generation to generation. The Hardy-Weinberg Equilibrium. 1pp:2pq:1qq

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The Hardy-Weinberg Principle

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  1. The Hardy-Weinberg Principle By: Alex, Jared, Merrick and Larisa

  2. What Is It? A principle that states in populations in which ONLY RANDOM CHANCE is at work, allele frequencies will remain constant generation to generation

  3. The Hardy-Weinberg Equilibrium 1pp:2pq:1qq This is the EXPECTED GENOTYPIC RATIO

  4. Example- Blue Eyes & Brown Eyes Say eye colour is inherited by dominance. B is the dominant allele for brown eyes and b is the recessive allele for blue eyes • “p” is the frequency of the B allele • “q” is the frequency of the b allele • So, • The genotype BB = pp • The genotype bb = qq • The genotype Bb = pq According to the Hardy-Weinberg principle, the expected allele frequencies of this population should be 1pp: 2pq : 1qqgeneration after generation For this example, this can also be written as 1BB: 2Bb: 1bb

  5. So According To The Hardy-Weinberg Principle: • The genotypic ratio of this population should remain 1BB:2Bb:1bb generation after generation • But why isn’t this the case in nature?

  6. BECAUSE Any factor that causes allele frequencies to change leads to evolutionary change, and the Hardy-Weinberg principle does not apply

  7. Therefore, It Only Applies If: • Mutation is not occurring • Natural selection is not occurring • The population is large (a smaller population increases chance of genetic drift) • All members of the population breed • All mating is totally random • Everyone produces the same number of offspring • There is no migration in or out of the population

  8. Question Time 

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