Question

Under which of the fol le following conditions will the repressor pro 8. Which of the fo Lactose present/glucose present Lactose presentelucose absent Lactose absentelucose present 9. Under both conditions A and B c. Under none of the above conditions of the following is involved in regulation of the lac operon? repressor protein b. operator sequence (0) allolactose d. answers A and B are both correct s, all of the above are correct Which of the following statements regarding DNA mutations is FALSE? Exposure to mutagens increases the rate of mutation Frame-shift and base substitution are different types of DNA mutations DNA mutations always result in a change in genotype 4. DNA mutations always result in a change in phenotype . DNA mutations may cause cell fatality (death) U. The presence of glucose as an energy and carbon sourc inhibits the expression of a wide range of operons. This method of genetic control is referred to as? 4. quorem sensing b. catabolite repression constitutive expression (d chemotaxis glycolysis 11. Regarding bacterial conjugation, which of the following is FALSE? a. A recipient cell can remain F. 2. A donor cell forms a pilus structure e. A donor cell must possess an F factor. Direct cell to cell contact is required e. A donor cell becomes F-after complete conjugation. 12. Which statement(s) concerning transposons is/are TRUE? a. A complex transposon can carry genes from one chromosome to another. b. An insertion sequence is the simplest type of transposon. c. A complex transposon can carry genes from one cell to another. d. Answers A and B are correct e. All of the above are correct 13. Which one of the following statements is FALSE? a. Complex media can be used to grow any bacterial species. 5. Both eukaryotes and prokaryotes need sources of carbon, nitrogen, and phosphorus in order c. Bacteria grow best at a neutral pH of between 6.5 and 7.5 Some prokaryotic species may grow at temperatures above 100 degrees Celsius Bacterial species may need trace elements, such as iron, in order to grow 4. Which one of the following statements is FALSE? Bacteria need nitrogen for amino and nucleic acid synthesis. A photoautotroph uses the process of photosynthesis to "fix" CO, into organic glucose Microorganisms need phosphorous for nucleic acid synthesis. & All bacteria can (fix) nitrogen - use N2 directly from the atmosphere to meet their nitrog C. Some bacteria need organic vitamins in order to grow.

Answer 1

8) repressor protein inhibits the expression of the lac operon by binding to the operator and the allolactose is an inducer of the lac operon it activates the expression of the lac operon by inhibiting lac repressor, so lac repressor, operator and allolactose regulate the expression of genes so the answer is d) all of the above are correct.

9) mutagens are agents which cause mutation, exposure to mutagen increases the rate of mutation, frameshift mutations changes reading frame, base substitutions change a single codon, DNA mutations change the genotype, some mutations can be lethal, all mutations do not change the phenotype because silent mutations change the codon but do not change the amino acid, so the protein is not changed so the answer is d) DNA mutations always results in a change in phenotype.

10) glucose can inhibit the wide range of operons including lac operon, this is achieved by catabolite repression, the CAP protein which activates the expression of these operons require cAMP, glucose inhibits the production of cAMP so in the presence of glucose CAP cannot activate the expression of the genes. so the answer is b) catabolite repression.

(quorum sensing is the signaling between bacterias in a population, constitutive expression the genes are expressed always, chemotaxis is the movement depending on the concentration of chemicals, glycolysis is the breakdown of glucose to pyruvate)