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Equation 3 · Part 5 · Human Evolution Did Not Stop, and Medicine Is Now Steering It

=

qn+1=qn(1−sqn)1−sqn2q_{n+1} = \frac{q_n(1 - s q_n)}{1 - s q_n^2}
=

What this part means

The expressions on both sides represent the same quantity under the stated assumptions.

Its job in the formula

The equals sign connects the complete expression on the left with the complete expression on the right. Both sides must have compatible units.

The passage around this formula

It is worth working through what that channel can and cannot do to a population’s allele frequencies, because the arithmetic is genuinely calculable and genuinely modest. Consider a recessive disease allele at population frequency q , and suppose that in some fraction of pregnancies where both parents are identified carriers, embryo testing prevents the birth of an affected (homozygous) child while parents still have the same number of children overall, drawn from the surviving unaffected and carrier embryos. The standard discrete-generation recursion for selection with coefficient s against a fully recessive genotype is: qn+1=qn(1−sqn)1−sqn2q_{n+1} = \frac{q_n(1 - s q_n)}{1 - s q_n^2}. Set s = 1 , the theoretical maximum in which…

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Learn the underlying idea

An equals sign says that the expression on its left and the expression on its right have the same value under the stated definitions and assumptions.

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Sources cited in the article section

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