Analysis of Genes and Genomes

Rating:
Summary: Does its job well
Review:
The twenty-first century has rightfully been called the "age of biology", and draws on the laboratory techniques developed in the last half of the twentieth century. The advent of commercial products, medicines, and foodstuffs using the techniques of genetic engineering has resulted in an explosion of books and monographs that attempt, and usually succeed, in explaining these techniques to students and also to those curious about them. Compared to most of these books, this one gives a fairly rapid overview of the subject of genetic analysis and genetic engineering, but one can still gain a deep appreciation of the subject by its study. Many useful diagrams appear in the book, and the author gives useful summaries at the beginning of each chapter. This reviewer only read the last three chapters of the book, so this review will be confined to these.

The genetic engineering of plants is covered in chapter 11 of this book. This has become a very contentious topic of late, due to the perceived dangers of genetically modified crops. The author recommends, rightfully, that the potentially adverse side effects of these crops should be studied via careful experimentation. Genetically modified crops have been a contentious issue in the last few years, and the debate concerning their use and consumption has reached a level of vitriol that goes beyond all measurable bounds. This chapter puts the subject on a clear scientific foundation and readers who are interested in genuine scientific understanding of the genetic engineering of plants will benefit greatly from its perusal.

Why is it so difficult to get a foreign gene to be expressed in a mammalian cell in which it is inserted? This question is of great interest in biotechnology and is discussed in chapter 12 of the book. Another one of the more interesting topics in this chapter regards the existence of `immortalized' cells, which continue to divide even after being cultured. Two examples are mentioned, the HeLa cells derived from a woman who died of cervical cancer in 1951, and Chinese hamster ovary cells. Programmed cell death or `apoptosis' has been the subject of intense research in recent years, due to its importance in the curing of cancer. The author emphasizes the extreme difficulties involved in obtaining stable transfection in animal cell lines, and discusses several methods to make it more efficient.

The author continues the discussion of the genetic engineering of animals in chapter 13, after first reviewing some elementary embryology. This chapter is of particular interest to those readers who are interested in understanding the science behind stem cell research. First discussed is the production of transgenic animals using pronuclear injection. The author points out some of the consequences of this technique brought out by experiments with laboratory mice. One of these is the high concentration of growth hormone mRNA in their livers and growth hormone in their serum, resulting in mice of considerable larger size than their non-transgenic counterparts. The author lists some of the disadvantages in the technique, such as its inability to do gene knock-out, the difficulty in controlling the expression of the transgene, the fact that the expression of the transgene is not strictly inherited, and the occasional creation of a "mosaic" animal, where the transgene only occurs in certain organs and tissues of the animal. The creation of mosaic animals has resulted in patentable technology in recent years, so this technique, in various guises, does have practical applications.

Embryonic stem cells, defined by the author as being undifferentiated cells that are isolated from the inner cell mass of a blastocyst, are discussed next. Interestingly, embryonic stem cells can be maintained in culture indefinitely via cell divisions, and will remain undifferentiated as long as they grown at large distances from each other. The main advantage in using embryonic stem cells, according to the author, lies in their efficiency in homologous recombination. He points out though that non-homologous recombination does still occur, and to distinguish between cells that have integrated the DNA fragment homologously and those that have done so non-homologously, use is made of `ganciclovir', which after phosphorylation will result in inhibition of DNA polymerase activity. Cells that have undergone homologous integration will survive the ganciclovir treatment.

The author uses this discussion to motivate the concept of knock out genes, which he considers of extreme importance not only to the understanding of biology but also to the analysis of human disease. There are three classes of knock-outs depending on whether they are lethal to the organism, or either change its phenotype or not. The author also discusses the existence of `conditional' knock-outs, where there is no observable phenotype but arise when genes are acting in parallel pathways and consequently compensate for each other's functions. He also points out that knockout experiments take a considerable amount of time and are very expensive, but this will no doubt change in the upcoming years.

Nuclear transfer, certainly the most well known of the techniques in genetic engineering, is also discussed in this chapter. The cloning of mammals, via the transfer of cells from an embryo and fusing them with enucleated eggs, such as was done with sheep, is discussed in fair detail. The author points out the difficulties in producing viable offspring using nuclear transfer from differentiated adult cells. These include the inefficiency of the technique, abnormal offspring, telomere shortening and consequent shortening of life spans. Although cloning of other farm and domestic has been done successfully, the author exhibits justified caution in the cloning of human beings. However, if and when cloning can be shown to be a viable and safe technique for human asexual reproduction, it should definitely be an option for those individuals who have chosen it as their best method for reproduction.