Recombinant DNA technology：练习题

During the process of in vivo gene cloning, which enzyme is responsible for permanently joining the sugar-phosphate backbones of a DNA fragment and a vector, such as a plasmid?

Restriction endonucleases are enzymes that cut DNA at specific base sequences. Many of these enzymes produce sticky ends. Which statement correctly describes a feature of these sticky ends?

Artificial gene synthesis (using a gene machine) is a modern method for producing DNA fragments. Which of the following is a specific advantage of this method over using reverse transcriptase or restriction endonucleases?

Recombinant DNA technology involves the transfer of DNA fragments from one organism to another. Which property of the genetic code allows a gene from one species to be successfully transcribed and translated into a functional protein within a different species?

In the polymerase chain reaction (PCR), the mixture is heated to approximately \(95^{\circ}C\) at the start of each cycle. What is the primary purpose of this specific temperature stage?

Explain why a terminator region must be added to a DNA fragment before it is used for in vivo amplification.

In in vivo amplification, marker genes are often used. Explain how a marker gene for fluorescence allows scientists to identify transformed host cells.

A plasmid vector is treated with the same restriction endonuclease used to isolate a target DNA fragment. Explain the significance of using the same enzyme for both the vector and the fragment.

Recombinant DNA technology relies on the transfer of DNA fragments between organisms. Since the genetic code is universal, the recipient organism can translate the transferred gene to produce a functional protein.

(a) Define what is meant by the statement that the genetic code is universal. (1 mark)
(b) Identify the enzyme used to produce complementary DNA (cDNA) from an mRNA template and describe the role of DNA polymerase in making this fragment double-stranded. (2 mark)
(c) State one advantage of using artificial gene synthesis (a gene machine) to produce DNA fragments compared to using restriction endonucleases. (1 mark)

In the process of in vivo gene cloning, not all host cells will take up the recombinant plasmid.

(a) Describe the process of transformation. (2 marks)
(b) Explain how marker genes, such as those for antibiotic resistance or fluorescent proteins, are used to identify which bacteria have successfully been transformed. (3 marks)