Question

You are studying aging in C. elegans (worms). You hypothesize that a particular signaling pathway might be important for promoting longevity (extending lifespan). You decide to perform an RNAi screen to knock down expression of each gene individually and examine the effect on adult lifespan. RNAi is especially powerful in C. elegans for genetic screens because, unlike many other organisms, you can feed them RNAi-containing bacteria to inhibit expression of specific genes. In your first experiment, you isolate eggs to obtain a synchronous population of worms and transfer the eggs to plates with RNAi-containing bacteria. Unexpectedly, you find that knock-down of many of the genes affect worm development and cause a larval arrest, preventing you from looking at adult lifespan. How could you redesign your RNAi genetic screen to get around this?

Answer 1

Since you are not getting viable organism from this experiment and it suggest that you have not designed a correct RNAi sequence (as it is completely inhibiting the function of gene and casuing lethality) to create gene knock down worms. First of all you need to see the sequence of that particular gene and design a construct that can inhibit the expression of desired gene partially or express significantly low as there are some important genes in the organism and if you knock out complete then they can cause lethality to the organism.

We can manipulate the worm with the help of bacteria (which contain plasmid with specific sequence to silence the expression of particular gene). Therefore, it is also recommended to alter an small portion of the gene or make them truncated (through just few sequences) so that they can not express normally and you may visualized the effect of your target gene in the organism as it will given you viable progeny.