What is DNA Transcription?
DNA transcription involves the formation of RNA from the DNA strand. DNA consists of complementary strands in which nucleotides are paired (A with the U and C with G). So, unlike DNA replication, only a segment of DNA and only one of the strands is copied into RNA. As the two strands have opposite polarity, that is, 5’ to 3’ and 3’ to 5’. The strand that 3’ to 5’ polarity is referred as the template strand whereas the other strand which has the polarity 5’→3′ is known as the coding strand. The coding strand has the same sequence as that of RNA (except thymine at the place of uracil).
The coding strand does not code for anything whereas the template strand does. The DNA-dependent RNA polymerase catalyzes the polymerization in the template strand only. The DNA segment where transcription starts is called a transcription unit, consisting of a promoter, structural gene, and terminator. The structural gene is flanked by the promoter and terminator in a transcription unit. The promoter is located towards the 5′ -end (upstream) of the structural gene and provides a binding site for RNA polymerase. Typically, the terminator, which is situated downstream of the coding strand at the 3′ end, marks the conclusion of the transcription process. In either the promoter’s upstream or downstream region, additional regulatory sequences may be found.
Difference Between Replication And Transcription
DNA replication and transcription are two different but related processes that take place inside the cell. Both involve DNA but differ in their role. For example-in replication DNA makes a copy of itself whereas in transcription DNA forms RNA. Both processes are complex as they require a variety of enzymes and proteins.