The Hardy-Weinberg Principle | Bio Basics š§
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Historical Context of Hardy-Weinberg Principle
š The principle's foundation traces back to Darwin's natural selection, but his contemporary belief in blended inheritance was challenged by Mendel's work on particulate inheritance (genes).
š°ļø Mendel's work was rediscovered around 1900 by Hugo de Vries and Carl Correns, leading to rapid advancements in genetics theory.
š G.H. Hardy (mathematician) derived the foundational mathematics in 1908 after being prompted by Punnett about the persistence of recessive traits.
š§ Although initially called Hardy's Law, it was discovered that German physician Weinberg published a more eloquent paper earlier in January 1908, and American geneticist William Castle published similar principles in 1903.
Hardy-Weinberg Equilibrium Equations
š¬ The principle asserts that allele and genotype frequencies remain constant over time in the absence of evolutionary influences (i.e., when specific assumptions are met).
š¢ For two alleles, the relationship is defined by the expansion of , resulting in the equilibrium equation: .
š The terms represent genotype frequencies: (homozygous dominant), $2pq$ (heterozygous), and (homozygous recessive).
ā¦ļø The sum of allele frequencies must equal one: $p + q = 1$, where $p$ is the dominant allele frequency and $q$ is the recessive allele frequency.
Solving Hardy-Weinberg Problems: A Step-by-Step Guide
šÆ The primary goal is often to calculate allele ($p, q$) and genotype () frequencies based on observed phenotypes.
1ļøā£ Step 1: Assign Alleles: Designate the frequency of the dominant allele as $p$ and the recessive allele as $q$.
2ļøā£ Step 2: Calculate $q$: Determine the frequency of the homozygous recessive individuals () by counting observed individuals ($12$ out of $1000$ in the example, or $0.012$). Calculate $q$ by taking the square root of ().
3ļøā£ Step 3: Calculate $p$: Use the relationship $p + q = 1$ to find $p$ ($p = 1 - q$).
4ļøā£ Step 4: Calculate Genotype Frequencies: Determine (homozygous dominant) and $2pq$ (heterozygous) using the calculated $p$ and $q$ values.
Key Points & Insights
ā”ļø The key to solving Hardy-Weinberg problems is identifying the number of homozygous recessive individuals, as this directly yields , from which all other frequencies can be derived.
ā”ļø Crucial error point: Recognize that the count of the recessive phenotype corresponds to , not $q$; students must take the square root to find the allele frequency $q$.
š” The value of the principle often lies in observing deviations: violating the assumptions provides crucial insights into evolutionary forces acting on a population.
šø Video summarized with SummaryTube.com on Nov 24, 2025, 02:32 UTC
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The Hardy-Weinberg Principle states that allele and genotype frequencies in populations remain stable over time, given certain assumptions. What assumptions? What does the principle mean? And how do you SOLVE those Hardy-Weinberg PROBLEMS? Everything shall be revealed in this video - with some penguins of course. They make everything go down easier.
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Links to Videos Mentioned:
Mendelian Genetics: http://youtu.be/xtJwHytHRfI
How to Solve Genetics Problems: http://youtu.be/Qcmdb25Rnyo
Solution for the additional problem I showed at the end:
Allele Frequencies:
q = 0.04
p = 0.96
Genotype Frequencies:
homozygous dominant: 0.92
Heterozygous: 0.08
Homozygous recessive: 0.002
Answer to the additional problem step-by-step: http://www.penguinprof.com/uploads/8/4/3/1/8431323/solving_hardy-weinberg_problems.pdf
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Video Details:
Population Genetics:
The Hardy-Weinberg Principle
You need to know:
gene vs. allele
gentoype vs. phenotype
understanding probabilities (and vs. or)
Punnett Square
Hardy-Weinberg Principle
Timeline of Discoveries
Darwin, Mendel, DeVries, Correns
Hardy, Weinberg, Castle
Mendelian Genetics Gets HOT
Particles are inherited!
Traits aren't blended!
Cambridge opens a department of Genetics
So What's it All About?
It's about frequencies
When talking about population genetics, we are interested in the prevalence of a particular allele or genotype in a population
The Hardy-Weinberg Principle States:
Frequencies of alleles and genotypes in a population will remain constant over time in the absence of other evolutionary influences
Assumptions
Organisms are diploid
Generations are non-overlapping
Population must be large
No immigration or emigration
No mutation in the gene of interest
No natural selection occurs (individuals reproduce at equal rates)
Mating is random
Alleles and Allele Frequency
Penguin Prof Helpful Hints
The Sum of All Possible Outcomes MUST Equal 1
p+q = 1
ALLELE FREQUENCY
2 Alleles = Genotype
p2 + 2pq + p2 = 1
What if There are Three Alleles?
(p, q and r)
Sample Problem
In a population of 1,000 penguins, 12 have blue feet. Find the frequency of the blue allele, the yellow allele and the frequencies of the three possible genotypes in this population.
Solving Hardy-Weinberg Problems
Assign the alleles
Frequency of the dominant allele is 'p'
Frequency of the recessive allele is 'q'
Calculate q by taking the square root of the number of homozygous recessive individuals
Calculate p (the allele frequencies must equal 1, so p = 1 ā q)
Use p and q to calculate the other genotype frequencies:
frequency of homozygous dominant individuals = p2
frequency of heterozygous individuals = 2pq
frequency of homozygous recessives = q2
This may help:
Hardy-Weinberg Punnett Square
Try Another One...
In a population of 130,000 magical mice, green fur is dominant over orange. If there are 300 orange mice in a population of 130,000, find the following (assume population is in Hardy-Weinberg equilibrium):
1. Frequency of dominant (green) allele
2. Frequency of recessive (orange) allele
3. Frequency of each genotype
Full video URL: youtube.com/watch?v=oG7ob-MtO8c
Duration: 11:40
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šRelated Tags
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AI Summary of "The Hardy-Weinberg Principle | Bio Basics š§"
Get instant insights and key takeaways from this YouTube video by ThePenguinProf.
Historical Context of Hardy-Weinberg Principle
š The principle's foundation traces back to Darwin's natural selection, but his contemporary belief in blended inheritance was challenged by Mendel's work on particulate inheritance (genes).
š°ļø Mendel's work was rediscovered around 1900 by Hugo de Vries and Carl Correns, leading to rapid advancements in genetics theory.
š G.H. Hardy (mathematician) derived the foundational mathematics in 1908 after being prompted by Punnett about the persistence of recessive traits.
š§ Although initially called Hardy's Law, it was discovered that German physician Weinberg published a more eloquent paper earlier in January 1908, and American geneticist William Castle published similar principles in 1903.
Hardy-Weinberg Equilibrium Equations
š¬ The principle asserts that allele and genotype frequencies remain constant over time in the absence of evolutionary influences (i.e., when specific assumptions are met).
š¢ For two alleles, the relationship is defined by the expansion of , resulting in the equilibrium equation: .
š The terms represent genotype frequencies: (homozygous dominant), $2pq$ (heterozygous), and (homozygous recessive).
ā¦ļø The sum of allele frequencies must equal one: $p + q = 1$, where $p$ is the dominant allele frequency and $q$ is the recessive allele frequency.
Solving Hardy-Weinberg Problems: A Step-by-Step Guide
šÆ The primary goal is often to calculate allele ($p, q$) and genotype () frequencies based on observed phenotypes.
1ļøā£ Step 1: Assign Alleles: Designate the frequency of the dominant allele as $p$ and the recessive allele as $q$.
2ļøā£ Step 2: Calculate $q$: Determine the frequency of the homozygous recessive individuals () by counting observed individuals ($12$ out of $1000$ in the example, or $0.012$). Calculate $q$ by taking the square root of ().
3ļøā£ Step 3: Calculate $p$: Use the relationship $p + q = 1$ to find $p$ ($p = 1 - q$).
4ļøā£ Step 4: Calculate Genotype Frequencies: Determine (homozygous dominant) and $2pq$ (heterozygous) using the calculated $p$ and $q$ values.
Key Points & Insights
ā”ļø The key to solving Hardy-Weinberg problems is identifying the number of homozygous recessive individuals, as this directly yields , from which all other frequencies can be derived.
ā”ļø Crucial error point: Recognize that the count of the recessive phenotype corresponds to , not $q$; students must take the square root to find the allele frequency $q$.
š” The value of the principle often lies in observing deviations: violating the assumptions provides crucial insights into evolutionary forces acting on a population.
šø Video summarized with SummaryTube.com on Nov 24, 2025, 02:32 UTC
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As an Amazon Associate, we earn from qualifying purchases
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