Question

Transcriptional machinery in eukaryotes

Answer 1

Answer:

Eukaryotic transcription occurs within the nucleus where DNA is packaged into nucleosomes and higher order chromatin structures. ... Protein coding genes are transcribed by RNA polymerase II into messenger RNAs (mRNAs) that carry the information from DNA to the site of protein synthesis.

Answer 2

Answer :-

★ In Eukaryotes

○ There are at least three RNA polymerase in the nucleus.

• RNA polymerase-I transcribes ribosomal RNA,
• RNA polymerase-II transcribes messenger RNA,
• RNA polymerase-III transcribes transfer of RNA.

○ The primary transcript hnRNA (Heterogenous Nuclear RNA) contains two types of segments the non coding introns and coding exons.

○ The primary eukaryotic mRNA transcript is non functional it undergoes three types of processing;

1) SPLICING : Where the introns are removed and exons are joined in a definite manner.

2) CAPPING : An unusual nucleotide methyl guanosine triphosphate is added to the 5’ end of the hn RNA.

3) TAILING : Adenylate residues are added (polyadenylation) at 3’end of hnRNA .

○ The fully processed hnRNA or mRNA is transferred outside the nucleus.