Three major types of RNAs are mRNA, rRNA, and tRNA. For each of the conditions below, predict the consequences in terms of the population of proteins being synthesized in a particular cell and the effects on individual proteins
(a) An acridine dye—induced mutation (adds or deletes single bases in DNA) leads to an mRNA for one protein-producing gene. The condition is heterozygous in the involved cell.
(b) A deletion (homozygous) that removes approximately half of the rRNA genes.
What will be an ideal response?
(a) Population of proteins: Half of the protein products of that gene will be defective, and the other half will be normal. Individual protein: The protein should show multiple amino acid substitutions "downstream" from the point of the mutation. If a nonsense triplet is introduced, the protein will be shortened in the substituted region. (b) Population of proteins: There would be an overall reduction in protein synthesis. Individual proteins: All of the proteins would be made in their normal form but at reduced levels.
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Gram-negative broth serves which purpose when used in the bacterial fecal culture?
a. Evaluation of general flora and predomi-nant species b. Selection of enteric pathogens such as Salmonella, Aeromonas, and others c. Inhibition of normal flora and selection of enteric pathogens d. Enrichment for enteric pathogens such as Salmonella and others
Which statement about steroid hormones in invertebrates and vertebrates is most accurate?
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Living organisms are distinct from nonliving
things by which of the following features?
a. continuous energy inputs b. complex molecular structure c. DNA that guides functioning d. sensing and responding to change e. all of these except complex molecular structure
The structures that will exchange nutrients and
wastes with maternal blood are indicated by a. A. b. B. c. C. d. D. e. E.