# Hardy Weinberg’s Principle

## Hardy- Weinberg Principle:

• In a given population one can find out the frequency of occurrence of alleles of a gene or a locus.
• This frequency is supposed to remain fixed and even remain the same through generations.
• Hardy-Weinberg's principle stated it using algebraic equations.
• According to this principle, allele frequencies in a population are stable and constant from generation to generation.
• The gene pool (total genes and their alleles in a population) remains constant. This is called genetic equilibrium.
• Sum total of all the allelic frequencies is 1.
• E.g., Consider, in a diploid, p and q are the frequencies of alleles A and a respectively.
• Frequency of AA= p2
• Frequency of aa = q2
• Frequency of Aa = 2pq
• Hence p+  2pq + q= 1 [binomial expansion of (p+ q)2]
• Change of frequency of alleles in a population disturbs Hardy- Weinberg equilibrium. This change is due to evolution.

### Factors affecting Hardy- Weinberg equilibrium:

• Gene migration: Gene flow from one population to another. Here gene frequencies change in both populations. Gene flow occurs if migration happens multiple times.
• Genetic drift: The gene flow by chance causes a change in frequency. Sometimes the change in frequency is so different in the new sample of the population that they become a different species. The original drift effect becomes the founder which is called the founder effect.
• Mutation: It results in the formation of new phenotypes. Over a few generations, these lead to speciation.
• Genetic recombination: Reshuffling of gene combinations during crossing over resulting in genetic variation.
• Natural selection: It is 3 types.
1. Stabilizing selection: Here, more individuals acquire mean character value, and variation is reduced.
2. Directional selection: Individuals of one extreme (value other than mean character value) are more favoured.
3. Disruptive selection: Individuals of both extremes (peripheral character value at both ends of the distribution curve) are more favoured.
If you would like to contribute notes or other learning material, please submit them using the button below.

### Shaalaa.com

Hardy Weinberg Principle Introduction [00:14:21]
S
0%