💡What is transcription? Write about transcription Unit.
💡RNA polymerase and their functions.
Transcription: The process of copying genetic information from one strand of DNA into RNA with the
help of RNA polymerase enzyme is termed as Transcription. In transcription only a segment of DNA & only one of the strand is copy into RNA.
Transcription Unit: A transcription Unit in DNA is define by three region in the DNA.
Transcription Unit: A transcription Unit in DNA is define by three region in the DNA.
1)A PROMOTER
2) Structural gene
3) A terminator.
The strand from which RNA is transcribe is known as a Template strand & the other DNA strand is known as Coding strand. RNA transcription always proceed to 5' to 3' direction. Hence the template strand will be 3' to 5' & coding strand will be 5' to 3'.
Promoter gene is attached with the 5 end of the coding strand & 3 end of the template stran. The promoter gene is a nucleotide sequence of TATA. Hence it is known as TATA Box. On the opposite side of the promoter gene there is a terminator gene. It is attached with 3 end of the coding strand & 5 end of the template strand.
RNA Polymerase: RNA polymerase are of 3 types. 1) RNA polymerase I{It synthesises rRNA}
2) RNA
POLYMERASE II [mRNA)
POLYMERASE II [mRNA)
3) RNA polymerase III[tRNA].
RNA polymerase is a large & complex enzyme. These enzyme composed of two α unit, one β unit, one β' unit, one w unit. & there are two subunit that bind & detouched from the enzyme according to the need
of the transcription process. The enzyme without these two sub unit is known as core enzyme. These two subunit are called as sigma unit & Rho factor.
Functions Of Unit & Sub Unit:
Α unit bind with the Initiation protein. Î’’ unit Binds with the DNA template. Î’ unit binds with the nucleotide. W Unit binds with the nucleotide.
Sigma unit: It attached with RNA polymerase to initiate trsanscription process.
Rho Factor: It helps in elongation & Termination of transcription.