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Unformatted text preview: Prelim 2 regrades must be submitted in writing to Shirley Soule (217 Stimson), no later than 2:00 on Friday 5/4. 1. (12 points) Define each of the following. a. regulon - (Nelson & Cox, p. 1094) A group of genes or operons that are coordinately regulated. b. open reading frame - (Nelson & Cox, p. 1039) A group of 50 or more contiguous non-overlapping nucleotide codons in a DNA or RNA molecule that does not include a termination codon. c. RNAi - (Nelson & Cox, p. 1111) A procedure in which double stranded RNA is introduced into cells in order to silence specific genes. d. specificity factor - (Nelson & Cox, p. 1083) These are proteins that alter the specificity of RNA polymerase for a given promoter. (The sigma subunit is an example of a specificity factor in E. coli ) e. DNA binding transactivator - (Nelson & Cox, p. 1104) Proteins that bind to enhancers or UAS sequences and thereby facilitate transcription. f. SNP - (Nelson & Cox, p. 324) " Single nucleotide polymorphisms" are single nucleotide differences in the genome sequences of individuals within a population. g. polycistronic - (Nelson & Cox, p. 288) An mRNA that codes for two or more different polypeptides. h. proteome - (Nelson & Cox, p. 325) The complement of proteins expressed by a genome. i. telomerase - (Nelson & Cox, pp. 1025-7) The enzyme that adds the non-coding repetitive (telomeric) sequences to the ends of linear eukaryotic chromosomes. j. RNA editing - (Nelson & Cox, p. 1040-1) A post-transcriptional process that changes the nucleotide sequence of an mRNA and therefore alters the protein product encoded by that mRNA (note splicing and post-transcriptional modifications described in Unit 7 are not acceptable here). k. Okazaki fragment - (Nelson & Cox, p. 952) The short RNA/DNA fragments generated during lagging strand synthesis. l. constitutive expression - (Nelson & Cox, p. 1082) Gene expression at a more or less constant level in virtually every cell of a multicellular organism, at all developmental stages, and/or under all conditions. BioBM330 2nd prelim 4/3/07 Answer Key 2 2. a. (2 points) Name the two most important measurements that were used to build the model of the structure of DNA? (Nelson & Cox, pp. 281-3) 1) x-ray fiber structure 2) chemical determination measurements that showed that the G=C and A=T in double stranded DNA b. (2 points) Name two types of interactions that stabilize the DNA double helix. (Nelson & Cox, p. 283) Hydrogen bonds Hydrophobic interactions (or van der Waal's interactions) c. (1 point) Explain why the diameter of the DNA double helix is uniform even though the nucleotide composition can be highly variable. Purines are made up of two rings whereas pyrimidines contain only a single ring. The size of both purine bases is similar as is the size of the pyrimidine bases. Because a purine (A or G) is always paired with a pyrimidine (C or T), the diameter of the double helix is uniform....
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- Fall '08