a)In transcription, what is meant by the phrases “coding strand” and “template s

Question

a)In transcription, what is meant by the phrases “coding strand” and “template strand”? How do they each relate to RNA? If given one or the other, could you provide the mRNA that would be produced from the DNA?

b)What is the function of bacterial sigma factors (be as specific as possible, naming all the things we talked about that a sigma like sigma70 can do)? What is a consensus sequence?

c)Can you describe what happens during bacterial mRNA transcription (what are the stages, what happens during each one, what are the major proteins involved)?

Explanation / Answer

Coding strand When referring to DNA transcription, the coding strand is the DNA strand which has the same base sequence as the RNA transcript produced. It is this strand which contains codons, while the non-coding strand contains anti codons. Template strand The terms template strand, sense strand, and coding strand are commonly used to describe one of the two strands of DNA, however the nomenclature is quite confusing because different authors have used these terms to describe both strands -- the strand copied into mRNA should be considered the template strand, but the other argues that the opposite strand which reflects the sequence in the mRNA should be considered the template because the corresponding codons are copied into protein. C) Transcription is the process of creating a complementary RNA copy of a sequence of DNA Both RNA and DNA are nucleic acids, Transcription can be explained easily in 4 or 5 steps, each moving like a wave along the DNA. RNA Polymerase moves the transcription bubble, a stretch of unpaired nucleotides, by breaking the hydrogen bonds between complementary nucleotides. RNA Polymerase adds matching RNA nucleotides that are paired with complementary DNA bases. RNA sugar-phosphate backbone forms with assistance from RNA polymerase. Hydrogen bonds of the untwisted RNA+DNA helix break, freeing the newly synthesized RNA strand. If the cell has a nucleus, the RNA is further processed (addition of a 3' poly-A tail and a 5' cap) and exits through to the cytoplasm through the nuclear pore complex.

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