In eukaryotic cells, a poly(A) tail is normally added to pre-mRNA, but not to rRNA or tRNA. With the use of recombinant DNA techniques, a protein-encoding gene (which is normally transcribed by RNA polymerase II) can be connected to a promoter for RNA polymerase I. This hybrid gene is subsequently transcribed by RNA polymerase I, and the appropriate pre-mRNA is produced, but this pre-mRNA is not cleaved at the 3′ end, and a poly(A) tail is not added. Propose a mechanism to explain how the type of promoter found at the 5′ end of a gene can affect whether a poly(A) tail is added to the 3′ end.

A common feature of many eukaryotic mRNAs is the presence of a rather long 3′ UTR, which often contains consensus sequences. Creatine kinase B (CK-B) is an important enzyme in cellular metabolism. Certain cells—termed U937D cells—have lots of CK-B mRNA, but no CK-B enzyme is present. In these cells, the 5′ end of the CK-B mRNA is bound to ribosomes, but the mRNA is apparently not translated. Something inhibits the translation of the CK-B mRNA in these cells. Researchers introduced numerous short segments of RNA containing only 3′ UTR sequences into U937D cells. As a result, the U937D cells began to synthesize the CK-B enzyme, but the total amount of CK-B mRNA did not increase. The introduction of short segments of other RNA sequences did not stimulate the synthesis of CK-B; only the 3′ UTR sequences turned on the translation of the enzyme. On the basis of these results, propose a mechanism for the inhibition of CK-B translation in the U937D cells. Explain how the introduction of short…

Describe the initiation step of bacterial transcription (make sure to include important enzymes, parts, and sequences in your answer) up to the beginning of elongation. What are three ways that transcription differs between bacteria and eukaryotes? (I'm not looking for types of RNA modification, just in terms of transcription)

Using the transcription unit diagrammed below, in which exons are represented by blue boxes and introns are represented by the connecting lines.  You discover a single base deletion in region E of this DNA sequence. Regarding transcription, this mutation will likely: 1.) Result in an alteration to the mRNA sequence. 2.)Have no effect on transcription or the mRNA sequence 3.)Prevent transcription at the TATAA box 4.) Result in an increase or decrease in the amount of mRNA transcribed

Although the genetic code is universal, a few organisms such as Paramecium have a slightly modified version in which UGA, a stop codon for most organisms, codes for tryptophan in Paramecium. Suppose that the researcher wanted to make an in vitro translation system using all of the components from Paramecium. Which of the components, if any, would she need to replace in order to have an in vitro system that was universal? Possible Answers: A. She would need to leave out the P site. B. She would need to leave out the termination factor proteins. C. She would need to leave out the tRNA that recognizes UGA. D. She would need to leave out the ubiquitin