2. You have cloned the 4 bacterial species. Now you want to determine which one

Question

2. You have cloned the 4 bacterial species. Now you want to determine which one can degrade BA You therefore, mix pure BA with these bacteria and wait for a day. Then you measure the decrease in BA levels in each bacterial culture. You find out that species #3 (Sp3) reduces BA levels, and therefore, you decide that the gene which can degrade BA must be present in the genome of Sp.3. To find out which gene degrades BA, you make a microarray platform, with oligonucleotides corresponding to each gene of Sp.3. Then you perform the following experiment where you add the shown amounts of BA to Sp.3, and wait for the shown times, and you measure how much of BA is degraded. Results are shown in the below table. Experiment Nr BA added Time waited BA remaining at the end of experiment 10 12h 10 10 24h 0.0001 10 6h You then obtain mRNA from Sp.3 treated with BA for the times shown above and perform a microarray experiment. Some of the genes and the expression changes of these genes are shown below Time1h 6h 12h 24h Gene Nr 20 50 250 35 75 1000 37 500 100 250 1000 1500 35 Which of these 5 genes would you pick to study further (clone and purify) as a candidate BAse? Please explain your logic briefly

Explanation / Answer

The information suggess that BA is digested by the gene product from the bacteria. The tabulated data clearly suggests that the concentration of BA left i n the media after 24 h is minimum in amount. Thus, it is very clear from the first table that these cells required a time period of atleast 24h to completely degrade the BA.

Now, looking at the second table, it can be understood that the as the concentration of BA decreases in the media, the gene required for generation of BAse should also increase gradually with time. The second table clearly suggests that the expression levels of two genes, 3 and 4 increased with time. However, careful observation suggests that only the expression pattern of gene 4 increased gradually with time without fluctuations and hence, the gene 4 must be directly involved in degradation of BA in the media.

Thus, thus explains that the synchronization of decrease in concentration of BA in the media with simultaneous increase in gene expression of gene 4 clearly demonstrate the direct involvement of this gene in degradation of BA.

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