Review questions answers

Review questions

26.1 The term gene therapy refers to a method

A.      For the treatment or prevention of disease by allowing the patient’s cells to produce specific therapeutic proteins

B.      For the treatment of genetic as well as acquired or chronic diseases

C.      Which allows production of therapeutic protein or inhibition of abnormal protein production

D.      Which allows somatic or germ-line cells to produce therapeutic/ reporter proteins

E.       All of the above

26.2 Gene therapy has a great potential because

A.      It can control the intracellular production of a gene product in response to a disease

B.      It can restrict the availability of any gene product to specific sites in the body

C.      It can deliver sustained therapeutic protein levels over a prolonged period

D.      Gene expression can be turned on or off in response to the ben-efits of treatment

E.       All of the above

26.3 Define gene, gene expression, transcription and translation. What are the three basic components of a gene medicine?

26.4 What is antisense therapy? What are the types of antisense com-pounds? What are the types of antisense oligonucleotides?

26.5 What is RNA interference? Define siRNA, shRNA, and miRNA.

26.6 Describe the essential feature of a gene expression system.

26.7 Describe the influential factors for the development of nonviral gene therapy products.

Answers:

26.1 E.

26.2 E.

26.3 Genes are made of DNA, which contains information about when and how much of which protein to produce, depending on the functions to be performed. Gene expression is the process of transcription of DNA into RNA and translation of mRNA into proteins. The antisense strand of DNA is used as a template for transcribing enzymes that assemble mRNA, a process called transcription. Then, mRNA migrates into the cytoplasm, where ribosomes read the encoded information, its mRNA’s base sequence and, so doing, string together amino acids to form a specific protein. This process is called translation.

26.4 Antisense therapy aims at inhibiting the existing but abnormally expressed genes by blocking the transcription of DNA or translation of mRNA into harmful proteins. The types of antisense compounds include antisense oligonucleotides (ODNs), peptide nucleic acids (PNAs), antisense RNA, aptamers, ribozymes, and siRNA. The types of antisense oligonucleotides include phosphodiester ODNs, phos-phorothioate ODNs, and methylphosphonate ODNs.

26.5 A gene expression plasmid is formed of circular double-stranded DNA molecules and contains a cDNA sequence coding for a ther-apeutic gene and several other genetic elements, including introns, polyadenylation sequences, and transcript stabilizers, to control tran-scription, translation, and protein stability.

26.6 The three important factors in the development of nonviral gene therapy products include the therapeutic gene, the gene expression system, and the gene delivery system. A therapeutic gene encodes a specific therapeutic protein, a gene expression system controls the functioning of a gene within a target cell, and a gene delivery sys-tem controls the delivery of the expression system to specific loca-tions within the body. Plasmid-based gene expression systems contain a cDNA sequence coding for a therapeutic gene and several other genetic elements, including introns, polyadenylation sequences, and transcript stabilizers, to control transcription, translation, and pro-tein stability. The gene delivery system distributes the plasmid to the desired target cells, after which the plasmid is internalized into the cells. Once inside the cytoplasm, the plasmid can then translocate to the nucleus, where gene expression begins, leading to the production of a therapeutic protein through the steps of transcription (synthesis of RNA from DNA into the nucleus) and translation (synthesis of protein from mRNA in the cytoplasm).