Transcription (Part-I)

INTRODUCTION: Every cell mainly contains three types of RNA-transfer RNA (t-RNA), ribosomal RNA (rRNA), messenger RNA (mRNA). Synthesis of RNA from DNA templates with the help of DNA dependent RNA polymerases is known as transcription. It occurs unidirectionally in which chain is synthesized in 5’ to 3’ direction. The segment which is transcribed from DNA is known as Transcription unit (Figure 28.1). In eukaryotes monocistronic transcription unit occur in which coding sequence presents for only one polypeptide. But in prokaryotes polycistronic transcription unit occurs in which coding sequence presents for more than one polypeptide.             

Figure 28.1 : Structure of gene