- August 24, 2016 at 9:45 am #18323Elena11Participant
During DNA transcription the 2 strands open and the RNA polymerase "reads" one of them (5′-3′) to synthesize mRNA, here is the point: the 2 strands are complementary but not equal, do they give 2 different mRNA that give 2 different amino acid sequences? Are these amino acid sequences releted with each other, coming from 2 complementary strands?
- August 24, 2016 at 10:23 am #116074claudepaParticipant
Hi. The 2 DNA strands are complementary according to the Watson Crick rules. When RNA polymerase 2 is activated by transcription factors binding on a given sequence of one strand of DNA (the coding strand) , it will synthetize mRNA complementary to the other strand of DNA. Therefore the mRNA sequence is similar (except U instead of T) to the DNA coding strand. However the so called non coding strand of DNA can be also be sometimes a coding strand if the sequences are recognized by transcription factors. The first to discover this in bacteria was a japanese researcher called Inouye. In that case the 2 mRNA are strictly complementary and can hybridize to form a mRNA double helix. Inouye has shown that the bacteria uses this system to regulate the omp genes which are genes responding at the membrane to the osmotic pressure. As far as I know the actual total sequencing of human genome has shown that a significant (10%, 20% ?) of the mRNAs are synthetized by the so called non coding strand.
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