BIOLOGY
Mosquito t-test
Tackling Malaria
In 2015, a genetically modified mosquito was produced with the ability to create antibodies to the plasmodium parasite.
It was predicted that if these mosquitos were released, then when feeding on infected blood they would destroy the plasmodium parasite before they could pass it on during their next blood meal.
The gene editing technology CRISPR-Cas9 was used to add genes to the genome of mosquito eggs and then samples of the modified mosquitos were taken. 99.5% of the offspring of the mosquitos were found to contain the gene.
Immunity to plasmodium was not tested and the mosquitos were never released into the wild.
In a similar experiment the ‘fitness’ of transgenic mosquitos was investigated and compared to non-transgenic mosquitos.
Populations of both mosquitos were maintained by feeding them on plasmodium infected mice.
The number of eggs produced by females in each population were counted.
Tackling Malaria
The null hypothesis is that the transgenic mosquitos have no advantage in fecundity (reproductive ability) over the non-transgenic mosquitos.
The alternative hypothesis is that the transgenic mosquitos have an advantage in fecundity as the mean number of eggs produced is ‘significantly’ greater.
Mosquito t-test
The t-test is to determine if there is a significant difference between the means of two populations.
0 sincostan sin-1cos-1tan-1πe xyx3x2ex10x y√x3√x√xlnlog ()1/x%n! 789+MS 456–M+ 123×M- 0.EXP÷MR ±RNDC=MC |
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| Number of eggs in clutch | |||||||
|---|---|---|---|---|---|---|---|
| Transgenic mosquitos | 115 | 170 | 162 | 189 | 201 | 194 | 159 |
| Non-transgenic mosquitos | 171 | 111 | 133 | 161 | 200 | 114 | 137 |
X1 = 170.0
X2 = 146.7
S1 = 29.18
S2 = 32.30
[Note: Your value of t should have the same level of precision as the critical values shown in the probability table; in this example the critical values are given to three decimal places.]
(7 - 1) + (7 - 1) = 12
t = 1.416
degrees of freedom = 12
At 12 degrees of freedom and using a significance level of 5% it can be determined that the t-test value of 1.416 is below the critical value of 2.179. We can therefore accept the null hypothesis.
The null hypothesis is that the transgenic mosquitos have no advantage in fecundity (reproductive ability) over the non-transgenic mosquitos.
The alternative hypothesis is that the transgenic mosquitos have an advantage in fecundity as the mean number of eggs produced is ‘significantly’ greater.
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