Question

34. Enhancer or Silencer element of DNA may be physically far away from promoter region. Yet, they can affect transcription rate. Explain how they can do it from a distance (3 pt). 35. List three differences of prokaryotic and eukaryotic transcription and transcripts (3 pt). 36. List (no explanation necessary) three major post-transcriptional modifications of eukaryotic mRNA (3 pt). 37. Explain two different transcription termination (4 pt)

Answer 1

Answer:- 34. Enhancer or silencer elements regulate transcription through the binding of a multitude of TFs that activate or repress transcription. These transcription factor binding elements influence transcription irrespective of location,they may lie proximal to the core promoter or several hundreds of base pairs from the TSS, or even on the other chromosomes. Variants of consensus sequences may dictate the strength of association with particular transcription factor, or preferential binding of specific demerisation partners. Sequences may also alter the conformation of a bound transcription factor, affecting its activities. May promote preinition complex formation,chromtin modifiers etc.

35. Prokaryotic transcription takes place in cytoplasm while eukaryotic transcription takes palce in nucleus.

RNA polymerase is a complex of five polypeptide while polymerase are a complex of 10 to 15 polypeptides

Doesn't require any protein or other factors for the initiation of transcription in prokaryotes, while a protein factor is needed for the initiation of transcription in eukaryotes.

36. In humans the large subunits contain 28 S, 5.8 S,5S RNA molecule and smaller subunit contains an 18 S RNA molecule.

Out of these RNA are carved out of different nucleases from a single primary transcriptive rRNA.

The 5S rRNA is synthesized from a separate RNA precursor outside the nucleolus.

37. There are two major types of termination strategy found in bacteria. Rho-dependent and rho- independent. The RNA contains a binding site for a protein called rho factor which binds to the different sequences and starts climbing up the transcript towards RNA polymerase.