Question

QUESTION 41 When a promoter is methylated, gene expressions O a silenced b.slowed. O c.activated O d. maintained O e enhanced QUESTION 42 The obvious advantage of the lactose operon system is that O a. lactose is not needed as energy for bacteria Ob the bacteria will make lactose only in the presence of the proper enzymes O c. glucose can substitute for lactose in the diet of intolerant persons. O d. lactose metabolizing enzymes need not be made when lactose is not present Oe.milk is not needed for the adult human diet QUESTION 43 What is the fate of the extra X chromosome in females? O a. The extra X chromosome is degraded after each cell division b.Both X chromosomes are maintained normally. c. The extra X chromosome duplicates Od. The extra X chromosome condenses O e. The extra X chromosome is deleted after fertilization and is not present in the remainder of cells in the body.

Answer 1

Answer 41: The correct answer is option 'A' i.e. silenced because methylation makes the DNA transcriptionally inactive. When methylation occurs at promotor, it regulates the gene expression either by recruiting the inhibitory proteins or stop the binding of transcription factors to DNA. As a result there will be no transcription and the gene will be silenced.

Answer 42: The correct answer is 'D' i.e., lactose metabolizing enzymes need not to be made when lactose is not present in cell. As lac operon is an inducible operon, hence it is in switch on state only when induced by lactose.

Answer 43: The correct answer is 'B' i.e. both the X chromosomes are maintained normally in females when an extra copy of X chromosome is present. In such situation of trisomy, the female is normal sexually, however, she may be taller than usual otherwise there are not much unusual physical changes.