HardyWeinberg Principle

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Hardy-Weinberg Principle
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Hardy-Weinberg Equation

• p2 2pq q2 1

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Hardy-Weinberg Equation

• Used To Study Genetic Drift In Populations
• Used To Calculate The Occurrence Of Alleles
  Within A Population. For Instance
• Lets Study PKU

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Hardy-Weinberg Equation

• PKU Is A Genetic Disease Where The A Newborn Is
  Unable To Metabolize Phenylalanine
• If Left Untreated, The Baby Will Be Severely
  Mentally Retarded By The Age Of One
• It Is Caused By A Homozygous Recessive Allele.

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Hardy-Weinberg Equation

• PKU Alleles
• Lets Call The Normal Dominant Allele K
• The Abnormal Recessive Allele k
• The Possible Genotypes Are
• KK Homozygous Normal
• Kk Heterozygous Carrier
• kk Homozygous Disease

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Hardy-Weinberg Equation

• Hardy Weinberg Selected The Following Letters
  To Represent The Alleles
• p The Dominant Allele
• q The Recessive Allele

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Hardy-Weinberg Equation

• Therefore
• p K Normal Dominant Allele
• and
• q k Recessive Allele
• Since p (K) q (k) Represent All The Alleles
• Then pq must equal 1

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Hardy-Weinberg Equation

• p q 1

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Hardy-Weinberg Equation

• Remember The Punnett Square?
• For The Child To Have PKU, Both Parents Have To
  Be Carriers Of The Recessive Allele
• Kk

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PKU Punnett Square
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Hardy-Weinberg Equation

• PKU Occurs In 110,000 Births
• That Means The Incidence Of PKU Is 1/10,000 or
  0.0001
• We Know A Baby With PKU Has A Genotype of kk
• We Know q Represents The Recessive Genotype
  So We Know q2 kk 0.0001

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Hardy-Weinberg Equation

• Therefore
• q Square Root (q2)
• q Square Root (0.0001)
• q 0.01

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Hardy-Weinberg Equation

• We Know That
• p q 1
• Therefore We Know That
• p 0.01 1
• Therefore We Know That
• p 1 0.01 .99

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Harvey-Weinberg Principle

• p2 2pq q2 1
• Substitute Solve
• (.99)2 2(.99)(.01) (.01)2 1
• 2pq 2(.99)(.01) 0.0198
• 2 of Population Carries The Recessive Allele