Question

A strain of bacteria possesses a temperature sensitive mutation in the gene that encodes the rho subunit. At high temperatures, rho is not functional. When these bacteria are switched to elevated temperature, which of the following effects would you expect to see? Explain your reasoning for accepting or rejecting these options.

1. Transcription does not take place at high temperature.

2. All RNA molecules produced are shorter then normal at high temperature.

3. Translation does not take place at high temperature.

4. RNA is copied from only one strand of the DNA for all genes in the genome at higher temperatures.

Answer 1

Reasons for accepting an rejecting options as below.

1. Rho terminates transcription in response to specific DNA signals transcribed into RNA called the rho-dependent terminators. There are two fundamental features of a rho-dependent terminator; a proximal Rho binding site called the 'rut site' (Rho utilization) and a distal sequence comprising the termination zone. that means transcription will occur but termination will be problamatic.

2. All RNA molecules will not be shorter because there are two methods for termination in bacteria and also rho dependent mechanism is mutated at high temperature which means RNA polymerase will not stop at stop site as rho is not there and hence will keep adding nucleotides and RNA molecule will be longer than the normal one

3.There is simultanious reaction in bacteria for transcription and translation and rho dependent cut is in the 3' end of RNA and as we know that is not going to make impact on translation process. As you can see in below image..

Ans 4. RNA is copied from only one strand of the DNA for all genes in the genome at higher temperatures.Yes it is true because RNA is copied form sense strand, which is the strand of DNA that has the same sequence as the mRNA, which takes the antisense strand as its template during transcription, and eventually undergoes translation into a protein. But temperature doesnt make any change here because this process is naturally occuring.