1. In what journal did this article appear? When?
Answer: In the journal "SCIENCE" Volume 208 on April 4, 1980
2. What is the primary purpose of this paper?
Answer: The purpose of this paper is to explain how the recombinant bacterial plasmids that contain DNA which are complimentary to the human preproinsulin messanger RNA work and how they have been constructed.
3. What is the structural difference between insulin and proinsulin?
Answer: The structural differen ce between insulin and proinsulin is that insulin consists of two polypeptide chains, the A and B chains these chains are linked by disulfide bonds. The protein in insulin is synthesized as a single precursor polypeptide, and so in this process the A and B chains join via the C peptide. Proinsulin is different than insulin because it is contained within an even larger polypeptide called preproinsulin. Preproinsulin was first identified by in vitro translation of the messenger RNA derived from pancreatic B cells.
4. What is complimentary DNA (cDNA)?
Answer: Complimentary cDNA is derived from human insulinoma mRNA, this mRNA was isolated from 100mg of human insulinoma tissue and by the guanidinium thiocyanate procedure and also the double-stranded cDNA was prepared and cloned into the Pst site of pBR3222.
5. What is meant by the "polyA tail" or "polyoderylation" of a gene?
Answer: The polyAtail or polyadenylate is a tract of 40 nucleotides which are part of the nucleotide sequence of pH13.
6. What is meant by the statement that "insulin A and B chains are highly conserved"?
Answer: The statement that insulin A and B chains are highly conserved means that they are not variable such as the C peptide chain.
7. Which chain is most highly conserved?
Answer: Not one chain but parts or regions of both the A and B chain.
8. What do the researchers believe is the purpose of the C chain?
Answer: Researchers believe that the C peptide chain helps the proinsulin molecule to assume its correct three-dimensional conformation and that the greater amount of amino acid sequence variablility in the C peptide chain does not interfere with its ability to function in this manner.
9. Why does it make sense that the C chain is more variable(less highly conserved) than the A chain and B chain?
Answer: It makes sense that the C chain is more variable because first and second position codon changes are more prevelent than in the A and B chains.
10. What do the researchers believe is the purpose of the pre-peptide(D chain)?
-I was unsure of the answer so I am going to ask in class on Monday-
11. How does the human preproinsulin gene differ from rat preproinsulin (Rat I and Rat II)?
Answer: The human Preproinsulin gene differs from rat preproinsulin because the human sequence differs by only one nucleotide.
12. What is the first codon in the coding region of the gene(at the start of the pre-peptide) and what is the first amino acid in the polypeptide?
AUG
Saturday, March 13, 2010
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