E.coli lac operon control by lac I is. 64. a) negative inducible b) negative rep
ID: 270679 • Letter: E
Question
E.coli lac operon control by lac I is. 64. a) negative inducible b) negative repressible n c) positive inducible d) positive repressible 65. What is the function of allolactose in regulation of the lac operon? a) inducer b) repressor c) activator d) promoter e) regulatory protein 66. What histone modification typically increases expression of a gene? a)phosphorylation b)methylation c) acetylation d) polyadenylation True - a, False b 67. RNA can be analyzed using Northern blots. Multiple Choice 68. Amutation changes a codon that specifies an amino acid into one that terminates translation. a) missense b) nonsense c) silent d) neutral e) reverse 69. A purine being replaced by a different purine is called a c) neither of these a) transition 70. The Ames Test assumes that both cancer and b) mutations b) transversion result from DNA damage. a) repair c) histidine d) bacteria e) operons 71. Within the Ames Test, a plate withcolonies most likely contains the strongest a)o b)3 c15 d) 25 e) 35 True a, Falseb 72. The bacteria used in the Ames Test have fully functional DNA repair abilities. 73, Liver enzymes are incorporated in the Ames test to determine if it is possible for some chemicals to be processed/converted into mutagens.Explanation / Answer
64. A regulatory repressor protein is normally bound to the operator in -ve inducible operons, which prevents the transcription. While if an inducer is present, it binds to the repressor and changes its conformation so that pol is not able to bind to the operator, and gene expresses.
The lac operon is a negatively controlled inducible operon, and thus, option 1st is correct.
The transcription of the operon normally takes place (switched on mode) in negative repressible operons, because repressor is not able to block the site.
The activator proteins are normally unable to bind to the relevant DNA in positive inducible operons
The activator proteins are normally bound to the relevant DNA in positive repressible operons.
65. allolactose act as activator of operon which is designated as inducer molecules.
66. histone modification in covalent structure of histone, including methylation, phosphorylation, acetylation, ubiquitylation, and sumoylation, after the translation process. Therefore, option A, B C are correct.
67. In northern blotting, we use to detected the particular RNA species from mixtures of RNA. (TRUE).
68. mutant change the codon that specific an amino acid in to one that termination codon. The presence of a nonsense codon causes termination of translation (ending polypeptide chain synthesis). (option B)
69. In point mutation, while purine is replaced by purine is called transition while purine replaced by pyrimidines is call transversion. Thus, the Option A is correct
70
The Ames test is a widely employed method that uses bacteria to test whether a given chemical can cause mutations in the DNA of the test organism. Therefore, right option is B
71. In Ames test, 8 well plates is used in which 3 contains stronger dose.
72- some proposed that organisms can tolerate low level of mutagens due to protective mechanisms such as DNA repair, TRUE
73- rat liver enzymes can be added in an attempt to replicate the metabolic processes' (TRUE)
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