48) A molecular clock for evolution is based on the frequency of change in the a
ID: 3165502 • Letter: 4
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48) A molecular clock for evolution is based on the frequency of change in the a. b. c. d. fossil records of organisms. cellular structures of organisms nucleotide sequences in the genomes of organisms. enzymatic activities of organisms. 49) Repression and induction of enzyme biosynthesis occurs at the level of a. pre-transcription b. transcription. c. translation d. post-translation. 50) In negative control of transcription, how does the presence of a co-repressor like the amino acids tryptophan or arginine affect transcription? a. b. c. d. The co-repressor binds to the operator, preventing transcription The co-repressor causes the repressor to bind to the operator, preventing transcription. The co-repressor binds to the promotor, preventing transcription. The co-repressor prevents the repressor from binding to the operator, preventing transcription 51) In the scientific name Staphylococcus aureus, Staphylococcus is the a. class genus c. specific epithet. d. family 52) A prokaryotic species is defined as a population of cells with identical characteristics. population of cells that share 97% of their characteristics. group of related organisms that can interbreed when mature group of organisms that grow as single microscopic cells None of the above a. b. c. d. e.Explanation / Answer
48. c. nucleotide sequences in the genomes of organism.
Molecular clock is used to determine the changes in the nucleotide sequences using which the divergence of life forms during the course of evolution can be studied.
49. b. Transcription
Repression occurs when the effector molecules prevent the binding of polymerase to the promotor region, thereby preventing transcription. Induction occurs when the effector molecules facilitate the binding of polymerase to the promotor region thereby enhancing transcription.
50. b. the co-repressor causes the repressor to bind to the operator, preventing transcription
The co-repressor acts as an effector to convert the aporepressor into the active repressor. When the co-repressor binds to the aporepressor, it induces a conformational change that converts the regulatory protein into a holorepressor. The holorepressor binds to the operator region and blocks the attachment of RNA polmerase to the promoter thereby shutting off the transcription.
51. b. genus
According to the binomial nomenclature of the International Code of Nomenclature of Bacteria (ICNB), the first name denotes the genus which starts with a capital letter and is written in italics.
52. d. group of organisms that grow as single microscopic cells.
Prokaryotes are unicellular, microscopic organisms that lack true nucleus, mitochondria and other membrane bound organelles.
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