Do alleles frequencies always change from one generation to the next?

Question

according to the Hardy-Weinberg principle...do alleles frequencies always change from one generation to the next?

do genotype frequencies always change from one generation to the next?

cheers lol

Answer 1

Well, by the HWP frequencies remain constant, so I don't understand what you mean: HWP deals with populations, and the idea is that the frequencies will remain in equilibrium, so while one lineage may change the population remains static.

HWP states that genotype frequencies at any locus will remain constant all things being equal. Allele frequency will only alter if confounding factors are active within the population - anything that effects purely random breeding. Selection, mutation and inbreeding are all confounding factors, as they cause change in frequencies.

Random drift is always a factor, but can be ignored as a constant variable: it will be an error factor in any calculations.

Answer 2

It depends on how picky you want to be. Assuming that the population meets the criteria for equilibrium (no selection, no immigration/emigration, no mutation, random mating) then the possibility of random drift still is in force. In a large population such changes may be too small to measure reliably, so it would appear that the gene frequency is unchanged. On the other hand, the odds that it will remain exactly the same is very small, so you can argue that there will always be *some* change.

Answer 3

If the population is in HW equilibrium the allele frequencies will not change. If the population is not in HW equilibrium, they will. How much they will change depends on by what degree the conditions of HW equilibrium are not met.

For the record, it is impossible to meet all of the HW conditions:

Random Mating: this means NO mate selection at all. Every member of the population has an equal chance of mating with any other member of the population. To give you a crude analogy, truly random mating would be like putting all the eggs of a population in a bucket, adding all the sperm of the same population and giving it a stir.

No Mutation: DNA polymerase is error prone and many of the by-products of cellular metabolism are mutagenic, so even under the very best conditions you will always have mutation.

No Natural Selection: Humans have done a great deal to limit the effects of natural selection, however selection still applies to us. Any individual that is removed from the gene pool prior to reproduction has been "selected against". For example, how many people with Cystic Fibrosis reproduce as compared to the average for the population.

Migration: This can be controlled in theory, but in the real world it's very difficult.

etc.

So, in the end, there will be some fluctuation in allele frequency from generation to generation. How much depends on what population you are looking at, and what happend to that population.