About Pop. genetic heterozygosity & HWE

[proteinic]

Hi friends
First of all, sorry about my English it is not so fluent
I want to be an active member in this forum and also to make a friendships with other members
I am a student fourth year Zoology science and I am so interested in population genetic and bioinformatics
I read a lot of scientific articles in Population genetic and i,ve alot of questions about them
all most all of the methodology used in these researches depends on genotyping protein polymorphism or DNA for finding allele frequency, calculating heterozygosity and, estimating genetic variability Chi square and estimating the Hardy-Weinberg equilibrium HWE
What I couldn’t understand is the interpretation for the result, it always seems to be ambiguous and sometime with no meaning
For example something like heterozygosity or allele fre. what kind of things can informs us about the population
Yes I read that these are evolutionary parameters, by which we can know the selection pressure or genetic drift but if we have for example a heterozygosity 23% what can tell us about selection or about genetic drift? and also the same thing about HWE
How can read these figures ?
Could anyone summarize the use of these parameters in a simple way

And, I have an other question if we prove that a loci or a gene is in Hardy-Weinberg equilibrium HWE, does this mean that this gene cannot be used as a genetic marker or there is no hope for this Loci to be in Linkage-disequilibrium with any other gene

i think this is enough for now
if anyone have a question i also fully ready to answer him (if i know)

[oBWhat]

Hello
this is going way back years...
This is a great resource here on the topic:
http://users.rcn.com/jkimball.ma.ult..._Weinberg.html

To simplify things, the HW principle simply examines the presence of alleles in a population to assess their frequency.




The HW does not apply to the following situations when there is:

* mutation

* gene flow

* genetic drift

* nonrandom mating

* natural selection

Now to answer your question if you know the number of heterzygotes ie Bb is 23% then the percentage of homozygotes bb + BB must be 67%

So:
(p+q)^2 = p^2 + 2pq + q

# Let p represent the frequency of one gene in the pool and q the frequency of its single allele.

# So, p + q = 1

* p2 = the fraction of the population homozygous for p

* q2 = the fraction homozygous for q

* 2pq = the fraction of heterozygotes # In our example, p = 0.67, q = 0.23, and then you can solve by plugging in:

(0.67 + 0.23)2 = (0.67)2 + 2(0.67)(0.23) + (0.23)2

then continue. Please let me know if i made a mistake.

[proteinic]

Thank you O.Bwhat for the explanation and for the link that’s help a lot
Actually my problem was not with calculations as much as with the interpretations
I found another what I understand from that site we have to measure the HWE (expected frequency – observed frequency ) to have an idea about the selection impact on the population
now I know there is relationship between selection and HWE
if we found Hardy-Weinberg equilibrium that means there is no selection in that population
“If you think I am wrong plz tell me “
But what about genetic drift and how we can calculate it using heterozygosity for example??

The heterozygotes are just as successful at reproducing themselves as the homozygous dominants, but the homozygous recessives are only 80% as successful. That is, for every 100 AA (or Aa) individuals that reproduce successfully only 80 of the aa individuals succeed in doing so. The fitness (w) of the recessive phenotype is thus 80% or 0.8.
Their relative disadvantage can also be expressed as a selection coefficient, s, where
s = 1 − w
In this case, s = 1 − 0.8 = 0.2.
The change in frequency of the dominant allele (Δp) after one generation is expressed by the equation

I didn’t understand how they calculated the fitness coefficient W or 0.8 come from I tried many and it gave me different figures

(0.67 + 0.23)2 = (0.67)2 + 2(0.67)(0.23) + (0.23)2

then continue. Please let me know if i made a mistake.

I think there is a mistake here the left part does not equal the right part
(0.67 + 0.23)2 =1.8
0.67)2 + 2(0.67)(0.23) + (0.23)2 = 2.1082

Anywhy I will try to look for the answers from the web and and put them here in this thread in simple, clear and understandable way
If anyone have a question in Pop. Genetic plz don’t hesitate to ask