I only need help with H and I. 5) The UB food service hands you two organisms th
ID: 200025 • Letter: I
Question
I only need help with H and I.5) The UB food service hands you two organisms they found contaminating the drinks, and both organisms were isolated from both milk (lactose containing) and juice (glucose containing) substances, and thus can grow in both substances. We call these organisms S (Starbucks) and C (CVS), based on where they were identi isolate the You want to identify differences in transcription between the two organisms. You TOTAL RNA, and run the RNA for both S and C organisms on a gel. You identify two large bands on the RNA gel, with many small bands in between. These RNA appear to abundant and very large from a mass point of view A) Based on the lectures, these RNA that form these large, prominent bands, are most likely which type of RNA in the cell? Why? To further study transcriptional differences, in the S and C organisms, you add the antibiotic Rifampin, which inhibits transcription. You isolate TOTAL RNA and you measure the concentration of RNA. B) What is the simplest way to measure nucleic acid (RNA) concentration? How would you measure the change in RNA concentration? C) Do you expect the RNA to increase, decrease, or remain the same? Explain. he RNA from You want to compare transcription in the two organisms, S and C. You fractionate t both organisms, and you find that the S organism contains mRNA, whereas the C organisnm contains RNA, but not mRNA. D) What chemical features distinguish mRNA from other types of RNA? Does mRNA exist in both prokaryotes and eukaroytes? Explain You want to compare transcription under glucose (juice), lactose (milk), and mixed glucose with lactate conditions, in both S and C organisms. You find that when the C organism grow, glucose is first used, and then lactate is consumed. You remember the lecture on lac operon in class. In the C organism, under lactose containing conditions, and you use a probe for a specific DNA sequence that encodes for multiple genes involved in lactose metabolism. However, the RNA encoding these genes is not expressed under glucose containing conditions, only under lactose conditions E) How do you explain these findings based on your knowledge of the lac operon? F) What type of organism is C likely to be based on the above data (Bacterial (Prokaryotic) or Yeast/Mammalian (Eukaryotic)? Why? To fully understand transcription in organism C, you perform DNA footprinting. You find that RNA polymerase is bound to the DNA start site that encodes for a single RNA that is increased
Explanation / Answer
H. Transcription of a particular gene is initiated at DNA sequences known as the promoter. These are located near the transcription start site of genes(usually upstream the start site). prokaryotic promoters are two short DNA sequences located at -10 and -35 position upstream from the transcription start site.The sequence at -10 position(pribnow box) has the consensus sequence TATAAT and -35 element has the consensus sequence TTGACA. Opening of DNA takes place at -10 element as it is rich in A=T base pairs.
Each single mRNA can encode for multiple enzymes. Prokaryotes usually transcribe polycistronic mRNA that encodes for two or more polypeptides. The mRNA molecule has multiple open reading frames(ORFs) and each ORF is translated into a single polypeptide.
Upstream sequences do regulate transcription as these sequences are recognized and bound by RNA polymerase, and position the polymerase in the right orientation to start transcription of the target gene. Transcription is also regulated by proteins such as activators and repressors. Activators binds to enhancer sequences and facilitates binding of transcription machinery to the promoter thereby activating transcription. Repressors binds to operator sequences and blocks the attachment of RNA polymerase to the promoter thereby preventing transcription.
I. Alternate splicing is the differential splicing of introns giving rise multiple proteins from a single gene. Since introns are absent in prokaryotes, hence they do not undergo alternate splicing. If S is a prokaryotic organism, alternate splicing cannot be the mechanism of multiple isoforms.
If S is an eukaryote, then Alternate splicing may act as the mechanism for generation of Multiple isoforms. It is a regulated process in which particular exons of a gene are included or excluded from the final processed mRNA giving rise to proteins differing in amino acid sequence and also in their biological function. It is a mechanism of increasing the biodiversity of proteins that can be encoded by the genome.