Question

1. Describe the three stages in transcription in prokaryotes and note the functions of the enzymes that are involved for each. 2. Describe three ways in which transcription in in eukaryotes is different from that of prokaryotes. 3. At what stage of transcription do these alterations take place in? Initiation, Elongation or Termination? 4. Draw a prokaryotic gene with the following features: a. A promoter region with -35 and -10 consensus sequences. b. The start point of transcription with first codon c. The start point of translation (start codon). d. The stop codon of translation (stop codon). 5. Draw and label a Eukaryotic transcript that includes the following features: a. the 5' cap. b. a start codon c. two exons. d. one intron. e. a stop codon f. a polyA tail.

Answer 1

1.
1 prokaryotic gone start codon - Promoter TTGACG| TATAAT -35 Region -10 Region TAC Stop codon AUG VAR + Transcription start site Eukaryotic Transcrpt startcodon AUG Scap Exon INTRON stop Codon WAGAMA EXON

(1) Transcription in prokaryotes es having 3 steps 0 Thittadión Alongation 3 Terminaties (1) Juitiation: RNA polymerase initrates transcription at specific DNA Regions Called promoter. RNA polymeras Contains five subunits (a, a, B, B' and o) it is called holoenzyme. The J subunit of RNA polymerase binds to -35 region of promoter. when RNA Polymerase binds to promoter and initiates. transcription (2) Elongation: It begins with dissociation of the o subunit and the RNA Polymerase Enzyme proceed along the DNA Template as a result MRNA is synthesized in s toal direction (3) Termination: After alongation once the polymerase reakhes the stop codon it dissociates from the DNA template. It is of two types Rho-dependent and Rho independent Releasing factors RFI, RF2, RE3 are involved in termination of ARNA . In Rho-dependent termination the protein is involved. In Rho independent a hairpin loop is formed by C-G nucleotides and terminates the polymerase. 2 In Eukaryotes transcription takes place in nucleus and translation takes place in cytoplasm unlike in prokaryotes There are 3 types of RNA polymerases throlved in transcription RNA polymerase I, I, IL is responsable for franscribing mRNA TO TATA Box present 25-30 base pairs upstream hom the start site of transonption. TBP, TEND, TEIIH are required for transcription.