what is the hardy weinberg law? is it like mendels law, the exception rather than the rule? why?

Answer 1

This law is used in calculating rare population values for dominant/recessive alleles. They must be randomly crossing and not under strong selective pressure to be at equilibrium in the population. This means the population proportions will continue in successive generations until some new selection factor appears.
The equation is p+q=1
square both sides for p^2 + 2pq + q^2 = 1^2=1

f(p) is the frequency of the dominant allele
f(q) is the frequency of the recessive allele

Albinism a recessive trait is 1 in 2x10^4

q^2 = recessive genotype = 1/ 2x 10^4
q=.007
p=1- q = 1 - .007
p=.933

p^2 = f(p^2) = .933 x .933 = .87 -- dominant phenotype
2pq = f(2pq) = 2 x .933 x .007 = .013 - heteozygous
q^2= f(q^2) = .007 x .007 = 5 x 10^-5 - recessive

In a population of 6 million
.87 x 6x10^6= 5.2x10^6 are neither albino nor carriers.
78,000 are carriers & 300 are albino

Answer 2

The Hardy Weinberg equilibrium is a mathematical approach to the probability of finding a given gene in a population, assuming that the gene follows classical mendelian inheritance in a randomly breeding population.

It is flawed when applied to humans, because one of the core assumptions with this theory is that the population is breeding randomly. This lack of random breeding is why the probabilities of finding the genes for certain diseases (sickle cell, Tay-Sachs, etc) are much higher in some populations, and NOT the uniform number that the Hardy Weinberg equilibrium would predict.