Molecular Biology

Molecular Biology

Language: English

Pages: 912

ISBN: 0073525324

Format: PDF / Kindle (mobi) / ePub

A Doody's Core Title for 2015.

Molecular Biology, 5/e by Robert Weaver, is designed for an introductory course in molecular biology. Molecular Biology 5/e focuses on the fundamental concepts of molecular biology emphasizing experimentation. In particular author, Rob Weaver, focuses on the study of genes and their activities at the molecular level. Through the combination of excellent illustrations and clear, succinct writing students are presented fundamental molecular biology concepts.

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or luciferase, and let the easily assayed reporter gene products tell us indirectly the activity of the promoter. One can also use reporter genes to detect changes in translational efficiency after altering regions of a gene that affect translation. Gene expression can be quantified by measuring the accumulation of the protein products of genes by immunoblotting or immunoprecipitation. Filter binding as a means of measuring DNA–protein interaction is based on the fact that double-stranded DNA

colleagues demonstrated in 1996 that s is involved in pausing at position 116/117 downstream of the late promoter (PR9) in l phage. This implies that s is still attached to core polymerase at position 116/117, well after promoter clearance has occurred. Based on this and other evidence, an alternative view of the s-cycle was proposed: the stochastic release model. (“Stochastic” means “random”; Greek: stochos, meaning guess.) This hypothesis holds that s is indeed released from the core

labeled. The box in the small structure at lower right shows the position of the magnified structure within the RF complex. (Source: Murakami et al., Science 296: (a), p. 1287; (b), p. 1288. Copyright 2002 by the AAAS.) Two invariant basic residues in s regions 2.2 and 2.3 (Arg 237 [R237] and Lys 241 [K241]) are known to participate in DNA binding. Figure 6.36b shows why: These two residues (colored blue in the figure) are well positioned to bind to the acidic DNA backbone by electrostatic

(seen in the presence of the antibiotic) and an insertion state (seen in the absence of the antibiotic). Presumably, the substrate normally binds first in the preinsertion state (Figure 6.38b), and this allows the enzyme to examine it for correct basepairing and for the correct sugar (ribose vs. deoxyribose) before it switches to the insertion state (Figure 6.38a), where it can be examined again for correct base-pairing with the template base. Thus, the two-state model helps to explain the

sequence of bases. Watson and Crick saw a way to resolve this contradiction and satisfy Chargaff ’s rules at the same time: DNA must be a double helix with its sugar–phosphate backbones on the outside and its bases on the inside. Moreover, the bases must be paired, with a purine in one strand always across from a pyrimidine in the other. This way the helix would be uniform; it would not have bulges where two large purines were paired or constrictions where two small pyrimidines were paired.

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