Can dinosaurs be cloned?
In my local store, I found a rack of rather unusual greeting cards. One that caught my eye had an illustration of an insect in amber, with the words: CAUTION! Handle with extreme care! Opening the card made me jump - for an aggressive looking beast popped up as though to attack. The inside text said: Live dinosaurs!
Whilst this would have left people mystified a few years ago, most of today's consumers would have understood the meaning. Such was the impact of the dinosaur thriller Jurassic Park. But the film, and perhaps more so the book, has left people wondering: `Is it possible?'`Could extinct animals really be brought back to life?' By throwing more resources at the problem than funding agencies are finding for the human genome project, Jurassic Park paints a convincing picture . . .
To assess the challenge of cloning a dinosaur using fossil DNA, we should identify the key steps which must all have successful outcomes.
- Determine the complete DNA sequence for the extinct animal.
- Construct the specified molecules in the laboratory.
- Place the molecules in a nucleus within a suitable cell.
- Provide a suitable environment for development to take place.
With regard to step (1), the human genome project provides an indication of what has to be done in order to obtain the DNA sequence representing human beings - where samples for analysis are in plentiful supply. We may infer that a similar mega-project would be needed to capture the information sequences in any of the larger animals. But when genetic material is available only as degraded scraps, the chances of success are astronomically small - no matter how many resources are thrown at the problem. The longest sequences being reported from fossil plants and animals in amber are a few hundred base units long; the original DNA molecules are thought to be over a million times longer. Even if every insect in amber yielded a different base sequence, there would not be enough samples available to achieve a meaningful result.
The present state of DNA technology allows the construction of 30-40 base length strands which follow a specified sequence. Longer strands can be produced by joining shorter ones together - although the longer they get, the more difficult they are to control. Although this is a remarkable achievement, allowing people to talk of manufacturing an individual gene, there is an enormous gulf between what we can do and the manufacture of a full DNA sequence.
Step (3) brings us to the nucleus. The DNA must be tightly coiled around proteins called histones to form the chromosomes. The chromosomes must then be placed in a nucleus and the nucleus in a cell. The technology is available to clone certain organisms, but invariably the cells are not created in the laboratory! Preexistent cells are used, always having a close relationship to the animal being cloned. Any old cell will not do! The cell is not just a container: it is packed full of organic chemicals that interact with the specific DNA contained within the nucleus. Of great importance are the proteins which bind to the front end of genes and control their expression, which are often species-specific. Even if the DNA of an extinct animal were somehow to be obtained, and even if it could be encapsulated in a nucleus, there can be no expectation that a suitable host cell could be found to permit self-replication. To make matters more complicated, we do not yet understand some of the basic principles of development: although every cell in an organism is thought to contain all the genetic information relating to that organism, by no means can every cell be used to form a clone. The technical word here is totipotency. Only totipotent cells can develop into a mature organism. What's different about these cells? Until we know, even if we were able to put DNA in a cell, we could not guarantee that it would develop into an animal.
People have got used to the idea that DNA is a self-replicating molecule - but this is a misleading oversimplification. The cell is the only unit of life known to us that is self-replicating. Each component part, outside the cell, will disintegrate and be lost. But when all the parts are brought together, the cell is a living thing. It is like an exquisite jewel: a testimony to God's handiwork! The prevailing culture in Biology is reductionistic: that is, an object is believed to be the sum of its component parts, and if we understand the parts, we understand the object. But God's creation is not like this! To break out of the reductionist strait-jacket, we need a robust appreciation of intelligent design expressed in the construction and operation of every living thing.
Returning to our dinosaurs, and to step 4, the environment for development to take place must be recognised also as a critical factor. As the first cell divides and multiplies, it needs an environment that it can interact with - and a glass container will not do! `Test-tube' babies are falsely named - only a few things happen in a test-tube. Very quickly, the embryos are implanted in the mother's womb, because this environment has proved far too complex to recreate in a laboratory.
Professor Lewis Wolpert, one of our leading developmental biologists, has contributed something to these discussions. Responding to the thought that the Jurassic Park scheme for obtaining dinosaur DNA was not as far-fetched as first appeared, Wolpert declared in The Independent(Letters, 17 July, 1993): `Making dinosaurs from fossil DNA is science fiction, not science, and you should try to keep them distinct'.
The best science fiction has a good story and a link with visionary science, leaving plenty of scope for the imagination. Jurassic Parkis good science fiction! But why are people so willing to give credibility to these ideas? Is it because we've lost our sense of wonder at God's creation - and we think that man can be a creator too? Is it because few have any real idea about the complexity of living things?
We need to recapture a sense of the immensity of God's creation: we are paddling at the edge of a vast ocean. The psalmist declares: `How many are your works, O Lord! In wisdom you made them all'The Bible(Psalm 104, verse 24). The response in us must surely be one of worship and thanksgiving. `I praise you because I am fearfully and wonderfully made, your works are wonderful, I know that full well' (Psalm 139, verse 14). Such thoughts will preserve us from confusing science fiction with reality, and will counter any tendencies to reduce God's creation to the level of relative banality.
David J. Tyler (1993)
