Question

Given below is the sequence of steps of transcription in eukaryotic cell. Fill up the blank 1, 2, 3, 4 left in the sequence. 

Answer 1

Single nucleotide polymorphism (SNPS). 

1 – RNA polymerase 
2 – hn 
3 – processed RNA 
4 – tail

RNA polymerase is the primary enzyme needed for the transcription process. The enzyme creates a complementary RNA strand from a single strand of DNA. The promoter is assisted in binding by the RNA polymerase, which subsequently catalyses the polymerization of the template strand in the 5' to 3' orientation. The process is completed and a newly synthesised RNA strand is released once the terminal sequence is reached.

The process of transcription is enzymatically catalysed into three steps:

Initiation

The RNA polymerase attaches itself to the DNA molecule and then starts moving along the DNA strand until it identifies a promoter sequence. These points are known as transcription starts sites. The double helix structure of the DNA then unwinds and all the bases that are present on the DNA strands are exposed. This acts as a simple guideway for a new mRNA strand.

Elongation

To enable the growth of the mRNA strand, ribonucleotides are added to the template strand.

Termination

As the process continues, the RNA polymerase encounters a terminal sequence and the transcription automatically stops. The RNA polymerase then releases the DNA template.