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doi: 10.1242/10.1242/jcs.00658
Book Review |
Frederic Bushman
Cold Spring Harbor Laboratory Press (2002) 448 pages. ISBN 0-87969-621-4
$39 (paperback)
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DNA is the molecular repository of the programme of life. However, the DNA composition of an organism can be quite flexible. It seems that, rather often, DNA is transferred from one organism to another and that sometimes DNA can be stably incorporated in the recipient and thereby permanently change its genetic composition. This process is called `lateral' or `horizontal' gene transfer. Horizontal gene transfer is therefore the opposite of vertical transfer: vertically transferred genes are inherited from one's parents.
Lateral DNA Transfer: Mechanisms and Consequences, by Frederic Bushman, describes the mechanisms and consequences of lateral gene transfer; it covers the basic machinery of lateral DNA transfer, the rather well known transfer of antibiotic resistance genes between bacteria and the exchange of DNA sequences among phages and moves on to discuss transfer of retroviral genes. It also covers the role of lateral DNA transfer and the role it may have in the AIDS epidemic.
Bushman discusses differences regarding lateral transfer between prokaryotes and eukaryotes. DNA entering a eukaryotic cell must traverse not only the cytoplasmic membrane, but also the nuclear membrane, whereas in prokaryotes no nuclear membrane is present. Consequently, in eukaryotes there is a greater requirement for signals directing subcellular sorting. A fairly large part of the human genome is actually composed of retroviral genes: it can be hard to imagine that we are actually large walking carriers of fossil retroviral genes. The introduction of spontaneous mutations in mice has been linked to the insertion of genomes of a retrovirus or defective retro-elements, which shows that introduction of new genes may also lead to a new phenotype.
This well written book can be understood by undergraduate and graduate students as well as by established scientists. In fact, anyone that is interested in analysing genomes will appreciate this book. It discusses a subject that is currently not fashionable and that can still change the way we look upon evolutionary trees. Life would be simpler if the entire genome of every organism descended directly from the genome of its parents, but nature is, as always, more complex.
The last chapters of the book deal with lateral transfer in eukaryotic genomes and discuss the impact that transposons may have as well as aspects of evolution; for example, how exchange between bacteria and archaea may have occurred. It makes one wonder how much DNA is devoured by neighbouring organisms or cells. Lateral DNA Transfer: Mechanisms and Consequences also deals with a gypsy retrotransposom and reveals that feeding gypsy particles to Drosophila larvae may result in occasional transfer of gypsy genomes. In the light of lateral DNA transfer, it is interesting to note that a less talked about hypothesis by Darwin (pangenes) postulated that every cell in the body sends a miniature picture to the germ-line cells, which thereafter send these pictures (gemules) further through reproduction. This hypothesis may thus contain a grain of truth since certain genes seem to be able to enter the germ-line, possibly by the mechanism of lateral gene transfer. The question is then whether these transferred genes can be useful, harmful or do they become `junk' DNA. Bushman has assembled the basic knowledge of horizontal gene transfer and spiced the book with intriguing observations and ideas.
Center for Infectious Medicine, Karolinska Institutet, Sweden
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