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Equation 3 · Part 8 · Human Evolution Did Not Stop, and Medicine Is Now Steering It

subtraction

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

What this part means

Subtract the following term or group from the preceding one. A leading minus marks a negative quantity.

Its job in the formula

Subtract the following term or group from the preceding one. A leading minus marks a negative quantity.

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

Addition combines quantities; subtraction measures the signed difference between them. Parentheses show what is combined before the rest of the expression is evaluated.

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Sources cited in the article section

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