Question

17. Researchers can add several adenine nucleotides to the end of a strand of mRNA. What could be a practical application of this procedure?

18. A researcher develops a new form of polymerase chain reaction that can amplify long sequences of DNA. Is this technique likely to replace entirely the use of bacteria as cloning vectors? Why or why not?

19. You are studying DNA replication in bacterial cells. In one culture, you note that replication is not producing visible daughter cells. Your analysis shows that about 50% of the daughter cells appear normal, while 50% are volatile and do not form a double helix.
a) Draw and label a diagram that could account for your observation
b) If you centrifuged the DNA from this culture, what would you expect to see?

Answer 1

17)One practical application of adding adenine nucleotides to the end of a strand of mRNA is to increase the stability of the mRNA molecule, which can improve the efficiency of protein synthesis.
18)No, the new form of polymerase chain reaction is unlikely to replace the use of bacteria as cloning vectors entirely. This is because bacteria provide several advantages, such as efficient and reliable replication of DNA, and a large number of sites for insertion of foreign DNA. Bacteria are also easy to manipulate and culture, making them a convenient and well-established tool for molecular biology.
19a) To account for your observation, a diagram could show that the DNA replication process is being affected by a mutation or damage to the DNA replication machinery, leading to errors in the replication process. This could result in a mixture of normal and abnormal daughter cells.
b) If you centrifuged the DNA from this culture, you would expect to see a mixture of normal and abnormal DNA molecules. The abnormal DNA molecules would likely be shorter and fragmented, while the normal DNA molecules would form a characteristic double helix.