
'Anti-malarial mosquitoes' created using controversial genetic technology - jiangmeng
http://www.theguardian.com/science/2015/nov/23/anti-malarial-mosquitoes-created-using-controversial-genetic-technology
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carbocation
The controversy primarily comes from the applications of CRISPR-Cas.

In a sense the technology is like nuclear material: it can be used for ill; it
can be used for good; and it can cause harm even if trying to do good. But
this is also true of our more modest applications of human ingenuity and
power, such as civil engineering. I am choosing the nuclear parallel because
of the wide-ranging impact that facile genome editing will have - both
positive and, inevitably, with some negatives.

~~~
dekhn
Actually, _none_ of the controversy comes from applying CRISPR-Cas, since
that's just a boring technology part that simplifies something which could
have been done using more tedious mechanisms.

It's the gene drive part that's controversial.

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im2w1l
I had never heard about gene drive before.

It refers to making sure all children (and grandchildren etc) inherit a trait,
even though the trait isn't necessarily evolutionary beneficial for the
organism. The way this is implemented in this case by having a gene that codes
for proteins that insert the gene in chromosomes that do not already have it.

This means that by just releasing a few specimen with the gene drive, the
entire population can be gene modified in not-that-many generations. A year
may be sufficient for insects, since their generations are so short.

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ghshephard
"even though the trait isn't necessarily evolutionary beneficial for the
organism."

If the trait is negative, it will be selected out of the population. It's only
if it's beneficial, or neutral, that that it will spread. What's particularly
special about gene drive, is that it drives itself onto 100% of progeny,
rather than the 50% expected by traditional mendellian genetics.

~~~
im2w1l
If the trait is completely neutral it will double every generation (until
saturation is setting in). If the trait is like 10% negative then it will
instead increase by a factor of 0.9*2 = 1.8, which is still pretty quick.

Only if it is extremely negative, by more than halving amount of offspring,
will it be selected out.

That's in the short term. Presumably, some sort of resistance would evolve in
the long term.

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dekhn
These are all absurdly idealized models of actual population genetics. No
trait is truly neutral.

At the very least, this experimentation is likely to show some interesting
real-world population genetics that we can measure.

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brownbat
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.

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nshepperd
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
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...](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)),
we see that this will increase monotonically to p = 1 (all mosquitoes have the
modified trait).

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milkey_mouse
Mosquitoes 2.0 should suck malaria and give you blood.

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stephengillie
That's one way to do a blood transfusion. Imagine a cloud of tiny insects
surrounding 2 people, transferring blood from one to the other a drop at a
time.

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mike_ivanov
Those are called patent lawyers.

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afarrell
This is cool. Though, do they spread dengue fever or chikungunya?

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nl
No, but nor will they help against Dengue.

Actually, I'm not sure about chikungunya, but Malaria and Dengue is carried by
different species of mosquitoes. I _think_ chikungunya is carried by the same
species as Dengue, but I'm not sure if that is exclusive to that species.

~~~
XFrequentist
Not exclusively, but indeed the two main vectors for both dengue and
chikungunya are Aedes aegypti and aedes albopictus. Several other species are
at least somewhat capable of transmitting these viruses.

