43. The repressor protein of the lactose operon is synthesized a. only in the pr

Question

43. The repressor protein of the lactose operon is synthesized a. only in the presence of lactose b. only in the absence of lactose c. constitutively, both in the presence and absence of lactose 44 Mutations that arise in nature, from no particular artificial agent, are called a. oblique mutations b. induced mutations c. spontaneous mutations d. chromosomal aberrations e cosmic mutations 45. Life supporting genes that are always active in growing cells are a. housekeeping b. collective genes c. inducible d. heterochromatic 46. An example of a positive regulatory protein that helps turn on a gene or group of genes is a. lexA protein b. CAP protein c. CAMP d. lacI repressor e an enhancer sequence 47. Mutations that arise in a person's lifetime in one or more body cells are called a. cancerous mutations b. mutagens c. sporadic mutations d germline mutations 48. Rheumatoid arthritis is described as being 60% heritable. This means that a, 60% of the population has this disease bthe disease is 60% related to the genes you inherit but 40% to your environment or other factors C, the disease is 60% penetrant d, if someone in your family has the disease, you have a 60% chance of getting the disease too 49. A number of antibiotics have been identified that block the process of protein synthesis. Sparsomycin is one of these antibiotics that inhibits peptidyl transferase. What step of protein synthesis does this antibiotic inhibit? a initiation complex formation b. peptide chain formation c. peptide chain termination 50. X-ray diffraction data showed that the spacing between repeating units (nucleotides) along the axis of the DNA helix is a. 2.0 angstroms b. 3.4 angstroms c 20 angstroms d. 34 angstroms e. None of these are correct

Explanation / Answer

43. Lac operon repressor binds to the operator region of the lac operon in the absence of lactose. As a result RNA polymerase enzyme cannot bind to the promoter region and transcription of lac operon is turned off. In the presence of lactose, lac repressor is bound by allolactose. As a result the repressor protein cannot bind to the operator region. The promoter region is not blocked. RNA polymerase binds to the promoter region and transcription of lac operon genes is turned on. Lac repressor protein is constitutively expressed. So, the correct option is option C, constitutively, both in the presence or absence of lactose.

44. Spontaneous mutations arise naturally and they are not induced by mutagens. So, the correct option is option C, spontaneous mutations.

45. Some genes are constitutively expressed in a cell. These genes are known as the housekeeping genes and they are required for maintaining basic cellular functions. So, the correct option is option A, housekeeping.

46. The binding of positive regulatory proteins also known as the activator proteins is required to initiate transcription. Catabolite activator protein (CAP) is an example of a positive regulatory protein. So, the correct option is option B, CAP protein.

47. Mutations can be sporadic or germline. Germline mutations occur in the germ cells and are passed onto offspring by the parent. Sporadic mutations on the other hand are not due to inherited genes but these are as a result of environmental factors that induce random mutations in one or more body cells leading to cancer. So, the correct option is option C, sporadic mutations.

48. Rheumatoid arthritis is described as being 60% heritable. This means that the disease is 60% related to the genes you inherit but 40% to your environment and other factors. So, the correct option is option B.

49. Peptidyl transferase enzyme catalyzes the formation of a peptide bond between two amino acids during the process of translation. So, the correct option is option B, peptide chain formation.

50. The distance between repeating units along the axis of the DNA helix is 3.4 angstroms. So, the correct option is option B, 3.4 angstroms.

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