2 ms·

FTA: 99.5% of offspring received the trait. Anopheles females in tropical conditions take around 12 days to go from egg to adult. So if that's true, even if y

FTA: 99.5% of offspring received the trait. Anopheles females in tropical conditions take around 12 days to go from egg to adult. So if that's true, even if you could wave a magic wand and replace the entire mosquito population with these at one time, less than half of the population will still have the trait at the five year mark.[0] Compounding is a bastard. Though sure, the one-time magic wand doesn't resemble how this would be rolled out, but the general point is that the more frequently some species breeds, the harder it is to mess with. [0] 0.995^x = 0.5 -> x = 138.2 generations. 138.2 * 12 days / 365 = ~4.5 yrs.

nshepperd 11y ago
I'm not sure but I think the 99.5% figure here is for breeding modified mosquitoes with ordinary mosquitoes. That's the idea of the gene drive method. The spread of the gene has to be better than normal mendelian inheritance, otherwise it would never spread throughout the population in the first place...
- jnhnum1 11y ago
  Exactly. So suppose at some generation, the fraction of mosquitoes with the modified trait is p (and the unmodified fraction is 1 - p), and suppose that all mosquitoes are equally fit. A random child in the next generation will have the modified trait if: (a) both its parents are modified. This happens with probability p^2 (b) with probability .995 if one of its parents are modified. This happens with probability 2p(1-p), for a total probability of 1.99p(1-p). Overall, the fraction of modified mosquitoes in the next generation will have p^2 + 1.99p(1-p). Plotting this versus the identity function (http://www.wolframalpha.com/input/?i=%7Bp%2C+p%5E2+%2B+0.995*p*%281-p%29*2%7D+for+p+%3D+0+to+1 http://www.wolframalpha.com/input/?i=%7Bp%2C+p%5E2+%2B+0.995...), we see that this will increase monotonically to p = 1 (all mosquitoes have the modified trait).
- nonbel 11y ago
  They only got 2 modified mosquitoes out of 25,000 then bred the rest from those. I doubt normal Mendelian inheritance is applying here.
ghshephard 11y ago
From: http://www.nytimes.com/2015/11/24/science/gene-drive-mosquitoes-malaria.html http://www.nytimes.com/2015/11/24/science/gene-drive-mosquit... Because almost all the progeny carry the new genes, instead of just 50 percent as would be expected by Mendel’s laws of genetics, the inserted genes are expected to spread rapidly and take over a wild population in as few as 10 generations, or a single season. A large region, at least in principle, could be freed from malaria, which kills almost 600,000 people a year."

nshepperd 11y ago

I'm not sure but I think the 99.5% figure here is for breeding modified mosquitoes with ordinary mosquitoes. That's the idea of the gene drive method. The spread of the gene has to be better than normal mendelian inheritance, otherwise it would never spread throughout the population in the first place...

jnhnum1 11y ago
Exactly. So suppose at some generation, the fraction of mosquitoes with the modified trait is p (and the unmodified fraction is 1 - p), and suppose that all mosquitoes are equally fit. A random child in the next generation will have the modified trait if: (a) both its parents are modified. This happens with probability p^2 (b) with probability .995 if one of its parents are modified. This happens with probability 2p(1-p), for a total probability of 1.99p(1-p). Overall, the fraction of modified mosquitoes in the next generation will have p^2 + 1.99p(1-p). Plotting this versus the identity function (http://www.wolframalpha.com/input/?i=%7Bp%2C+p%5E2+%2B+0.995*p*%281-p%29*2%7D+for+p+%3D+0+to+1 http://www.wolframalpha.com/input/?i=%7Bp%2C+p%5E2+%2B+0.995...), we see that this will increase monotonically to p = 1 (all mosquitoes have the modified trait).
nonbel 11y ago
They only got 2 modified mosquitoes out of 25,000 then bred the rest from those. I doubt normal Mendelian inheritance is applying here.

ghshephard 11y ago

From: http://www.nytimes.com/2015/11/24/science/gene-drive-mosquitoes-malaria.html http://www.nytimes.com/2015/11/24/science/gene-drive-mosquit... Because almost all the progeny carry the new genes, instead of just 50 percent as would be expected by Mendel’s laws of genetics, the inserted genes are expected to spread rapidly and take over a wild population in as few as 10 generations, or a single season. A large region, at least in principle, could be freed from malaria, which kills almost 600,000 people a year."