fromdnatoproteinchapt12-文庫吧資料
2025-07-21 18:42本頁面
【正文】 NA replication. As in replication, a small section of the DNA double helix unwinds, and the bases on the two strands are exposed. RNA nucleotides (ribonucleotides) line up in the proper order by hydrogenbonding to their plementary bases on DNA, the nucleotides are joined together by a DNA dependent RNA polymerase enzyme, and a piece of mRNA is produced. ? UNLIKE what happens in DNA replication where both strands are copied, only ONE of the two DNA strands is transcribed into mRNA (remember that RNA is a singlestranded molecule). The DNA strand that is transcribed is called the template strand and is a copy of the DNA informational strand! Transcription Pol mRNA DNA 3’ 5’ RNA Polymerase ? Runs along DNA in a 5’ to 3’ direction (adding bases to the 3’ end) and forms mRNA ? Until it hits a STOP signal, falls off and mRNA is released…..DNA reseals… How does the RNA pol know where to start reading a Gene? ? The starting point of a gene is marked by a certain base sequence… called a promoter site. These sites are recognized by factors (termed SIGMA“) which recognize the promoter sites and tell the RNA polymerase where to begin. The RNA polymerase then carries out the process of transcription. ? Similarly, there are other base sequences at the end of a gene that signal a STOP to mRNA synthesis. A factor called RHO aids in terminating the process. The interaction of ‘rho’ with the RNA polymerase causes the enzyme to fall off the DNA template strand, thus stopping transcription. The Geic Code If DNA is a long repeating length of… ACTGAATTGCCCTTCATGGTCATGGCT How do you make a useful code??? How can you mak
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