Question

VERY EMERGENCE

B. In prokaryotes, there are consensus sequences before transcription start site on DNA and also before start codon in mRNA. Name these different consensus sequences and briefly describe their functions. (5 marks) ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

C. “When the energy charge in cell decreases, protein synthesis will slow down”. Explain this statement by listing the key steps affected. (5 marks) ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________

Answer 1

1.In prokaryote, there are many consensus sequence in prokaryotic genome. At Before transcription start site and before initiation codon in mRNA.

Consensus sequence at transcription site:-

Bacterial ptomoter share two region of consensus sequence, located 35 bp and 10bp upstream of transcription start site. The -35 consensus box has TTGACA sequence and -10bp consensus box also known as pribnow box has TATAAT sequence. This sequence play important role in RNA polymerase binding and initiation of transcription.

Consensus sequence at translation level :-

In mRNA a consensus sequence present at 3-10 nucleotide upstream of the start codon. It is a purine rich sequence of about six base pair, 5'AGGAGU-3'.This sequence also called Shine dalgarno sequence. This sequence helps to bind mRNA into ribosomal rRNA.

2.Energy storage in the cell in the form of Hight energy transfer compounds (like ATP/GTP) , and energy also available in the form of proton motive force. These types of energy require in the cell to perform synthesis of building blocks or structure of cell like protein synthesis and DNA replication, synthesis of nucleotide or Cytoskeleton.

When cellular energy decrease then rate of protein synthesis also decrease or will synthesis slow down. Because during protein synthesis high energy is required. We know that incorporation only one amimo acid residue into growing polypeptide required 4ATP/GTP. Now if we consider an E. Coli cell, in which the rate of translation is about 20 amino acid per second and it can synthesize a 300 residue polypeptide chain just 20 second at 300​​​​​​C ! So , for Only translation just 300 amimo acid residue required 1200 ATP+ /GTP required in just 20 sec. Now if energy change in cell decrease protein synthesis will slow down definitely.

Hope you understand. Best of luck.