Question

Consider the following statements about HARDY-WEINBERG PRINCIPLE and mark the correct option.

1. In a given population one can find out the frequency of occurrence of alleles of a gene or a locus. 

2. This frequency is supposed to remain fixed and even remain the same through the generations.

1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2

Answer 1

Correct Answer - Option 3 : Both 1 and 2

The correct answer is Both 1 and 2.

• In a given population one can find out the frequency of occurrence of alleles of a gene or a locus. Hence statement 1 is correct.
• This frequency is supposed to remain fixed and even remain the same through the generations. Hence statement 2 is correct.
• Hardy-Weinberg principle stated it using algebraic equations.
• This principle says that allele frequencies in a population are stable and are constant from generation to generation.
• The gene pool (total genes and their alleles in a population) remains a constant. This is called genetic equilibrium.
• The total of all the allelic frequencies is 1.
• Individual frequencies, for example, can be named p, q, etc. In a diploid, p and q represent the frequency of allele A and allele a.
• The frequency of AA individuals in a population is simply p². 
• This is simply stated in another way, i.e., the probability that an allele A with a frequency of p appears on both the chromosomes of a diploid individual is simply the product of the probabilities, i.e. p². Similarly of aa is q², of Aa 2pq. Hence, p²+2pq+q²=1.
• This is a binomial expansion of (p+q)². When frequency measured, differs from expected values, the difference (direction) indicates the extent of evolutionary change.
• Disturbance in genetic equilibrium, or Hardy- Weinberg equilibrium, i.e., change of frequency of alleles in a population would then be interpreted as resulting in evolution.
• Five factors are known to affect Hardy-Weinberg equilibrium.
  • These are gene migration or gene flow, genetic drift, mutation, genetic recombination, and natural selection.
• When the migration of a section of the population to another place and population occurs, gene frequencies change in the original as well as in the new population.
• New genes/alleles are added to the new population and these are lost from the old population.
• There would be a gene flow if this gene migration, happens multiple times. If the same change occurs by chance, it is called genetic drift.
• Sometimes the change in allele frequency is so different in the new sample of the population that they become a different species.
• The original drifted population becomes founders and the effect is called the founder effect.
• Microbial experiments show that pre-existing advantageous mutations when selected will result in the observation of new phenotypes. Over a few generations, this would result in Speciation.
• Natural selection is a process in which heritable variations enabling better survival are enabled to reproduce and leave a greater number of progeny.
• The critical analysis makes us believe that variation due to mutation or variation due to recombination during gametogenesis, or due to gene flow or genetic drift results in a changed frequency of genes and alleles in the future generation.
• Coupled to enhance reproductive success, natural selection makes it look like a different population.
• Natural selection can lead to stabilization (in which more individuals acquire mean character value), directional change (more individuals acquire value other than the mean character value), or disruption (more individuals acquire peripheral character value at both ends of the distribution curve).