Thursday, December 20, 2012

GM Mosquitoes #2

In the previous post, GM Mosquitoes #1  we had seen about the GM mosquitoes used for curing malaria. Now, we are gonna see about the GM mosquitoes designed for eradicating mosquitoes population!

Aedes aegypti is the mosquito species which spreads Dengue. Nowadays, people are suffering severely because of this Dengue. In most cases it just leaves with mild fever. But, in some cases, Dengue is deadly! So, to get rid of this great dengue nuisance, scientists had found a solution - GM mosquitoes!

We had seen that in the case of eradication of malaria by GM mosquitoes that scientists had made the mosquitoes resistant to malaria causing protist, but, here in this case of dengue the genetic modification is different.

In the case of dengue, male mosquitoes are made sterile and when they mate with the wild type female mosquitoes, their young ones are made unviable i.e they die before reaching adult stage. So, this reduces the population of mosquitoes by the death of new born young mosquitoes. (they use male ones as they don't bite and feed only plant products)

How the sterile males are made?

  • In one case, they say they are injecting an artificial gene into the male mosquitoes which makes them sterile.
  • In the other case, the male mosquitoes are exposed to gamma rays which causes mutation and makes the males sterile!
If this works out, the number of dengue victims will sharply come down. Moreover, you won't be bitten much!

Note: there is no medicine available for curing dengue.

  • Think, how harder it would be to separate male from female mosquitoes? This is the major disadvantage. :'(
  • Sudden elimination of one species may suddenly pave way for something worse ever! :(
  • If something goes wrong with this gamma ray mutation, even deadly species can come out! :O
Know this too!
  • Reports and articles I read says that already they had released these GM mosquitoes in the cayman islands.
  • Oxitec is the biotechnology company which is working on the production of this GM mosquitoes.
  • India (where i'm from) is also planning to use this technique for eradicating mosquitoes and reduce the number of dengue victims. 
After all, the Government or concerned authorities before releasing the GM mosquitoes into the environment, must inform the people living over there. Must get their feed backs! 

Releasing the GM mosquitoes with out prior information, won't be fine! This may lead to various ethical problems!

Just imagine!
They use males as they don't bite us (if they are biting us, then they won't try this at all, because we are always cautious that we would be affected) what if they affect plants? You  see, not a single mosquito is going to sit over a plant, when many mosquitoes sit and feed from plants, is it possible that they might affect the plants. Inturn, when we feed those plants, we will be getting affected?

Just I imagined this last paragraph, It's silly?  :)

Tuesday, December 18, 2012

GM Mosquitoes! #1

You are troubled at the mid-night? Your days are affected due to the lack of sound sleep? I can understand; The "mosquitoes", they are responsible for all this. We can bear with them if they are just biting and sucking a drop of blood, but, never, when they are injecting us with something like a "doctor", that too, which is never going to cure the disease like doctor's injection, but, going to give us disease.

Mosquito bats, liquids :( even with the help of these things, we are getting malaria, dengue, chikungunya :( :(

Scientists had found a solution for this greatest problem of our night!(nowadays daytime too)

GM mosquitoes, these genetically modified species are resistant to diseases like malaria. 

How malaria generally spreads!
As we all know, its because of mosquitoes, especially the female Anopheles mosquito which gets the virus when it sucks blood from an infected animal/human.

Half of the life cycle of the Plasmodium species (the malaria causing protist) happens in the  mosquitoes. So, to prevent the spread of Malaria (or any other mosquito spread disease) we must prevent the mosquito from getting affected by the disease.

HOW Genetic Modification done?
First, the mosquito should not get affected by the malarial protist i.e. it must be resistant against the plasmodium. When this is possible,  mosquitoes are not affected by plasmodium, thus humans are also not affected.

In the case of malaria: The gene responsible for fighting against malaria must be triggered. The gene is responsible for the production of a protein (they say SM1 peptide). This protein when produced, fights against malaria, i.e, the mosquito will become resistant to Malaria!

  • These GM Mosquitoes are weak, thus, reducing their chance of survival.
In the begining of the experiments conducted in the lab, there was 50/50 chances for GM and wild.
After 9 egg laying cycles they found this incresed to 70/30 for GM and wild.

You may wonder, here, GM has good surviving rate! yes, This is in the presence of malarial infection, but, when there is no malarial infection at all (i.e. the mosquitoes suck blood from healthy individuals only), the GM mosquitoes fail to outsurvive the wild type.

  • You know, these microbes are smart! 
There is every possiblity for resistance development. These Plasmodium's could modify themselves to infect the mosquitoes, thus, leading to the evolution of a new plasmodium speices which would be more powerful than the previously existing types. And, we can't control these new protists with existing medicines or treatments.

We can look about control of Dengue using GM mosquitoes in the next post very soon.

Read more about this @ 

Thursday, December 6, 2012

Cot Value Analysis

Wish you a good time :) Molecular biology! I was taught about "cot value analysis" in my molecular biology class. Here, you could read something, which I know about cot value.

Cot (C not (zero) t) value analysis:
This analysis uses the DNA denaturation and renaturation kinetics. This is used for measuring the repetitive DNA sequence in a given DNA sample. This analysis has application like separating repetitive sequences from mixture of DNA sample. Okay, let us discuss the procedure now.

Cot value = (C zero) * (Time) * (constant representing the effect of cation in the buffer on renaturation)
c zero -> DNA concentration (mol/l)
T - Renaturation time (sec)

  1. Denature the DNA sample by heating
  2. Cool and renature the sample, note renaturing extent (as cot value) at particular temperatures until a particular cot value is reached.
  3. Now, dilute this sample with sodium phosphate buffer- SPB (0.03M - at this buffer concentration the DNA bind to hydroxyl apatite properly)
  4. Bind this buffer solution with DNA to hydroxylapatite(HAP) column.
  5. 0.12M SPB is now used for eluting Single stranded DNA from HAP; Collect the Single stranded DNA.
  6. 0.50M SPB is then used for eluting double stranded DNA which is also collected.
  7. Volumes of Single and double stranded DNA collected is measured.
  8. 0.9ml of the centrifuged single stranded DNA is mixed with 0.1 ml of  10N KOH. This addition of KOH denatures the double stranded DNA (if present). Do this to the double stranded DNA sample also.
  9. Absorption values A260 (adjusted for light scatter at 360nm) are obtained for both the samples prepared (mentioned in the previous point)
Percentage of single stranded DNA could be calculated with the help of the following formula:

[(Vss x Ass) x 100] ÷ [(Vss x Ass) + (Vds x Ads)] = % ssDNA
Vss = total volume of single-strand fraction, 
Vds = total volume of double-strand fraction, 
Ass = A260(adjusted for light scatter) for the KOH-denatured single-strand fraction,
Ads = A260 (adjusted for light scatter) for the KOH denatured double-strand fraction.

  • The rate of renaturation of repetitive sequences will be high comparing the rate of renaturation of non repetitive or less repetitive sequences.
  • This is because, the possibility of a repetitive sequence to find it's complementary strand is greater than that of a non repetitive strand. (Hope you got it)
For detailed explanation refer "here"

Got any doubts? Kindly comment I'll try to answer.

Bye, Take CARE! :)