News & Views in 1999

Stochastic resonance increases the ability of some nonlinear systems to detect weak signals. Paddlefish are now shown to use stochastic resonance to locate and capture prey, implicating this phenomenon in animal behaviour.

Continuing this week's asteroidal theme, Daedalus has a plan for what we could do should a stray asteroid or comet smash into the Earth. His idea is that a defence system could be placed in a high Earth orbit. But this system would not consist of nuclear missiles -- rather, it would be another asteroid.

Although advances have been made in plant genetics, many species still cannot be studied owing to the lack of efficient methods for disrupting genes. This is no longer a problem for leguminous plants, thanks to the development of a technique for generating mutations. A marker transposon called Ac is inserted into the genome, and, if it is excised again precisely, it allows the affected gene to be sequenced with ease.

Many asteroids have a porous structure, which helps them absorb energy from collisions without being smashed to bits. This shows how planets might have formed, but could be bad news should an asteroid ever threaten Earth.

During the production of sperm, there is a 50:50 chance that any sperm will contain either copy of a chromosome pair. But there are exceptions. One is the so-called mouse t-haplotype, an unusual variant of chromosome 17 that can be inherited in up to 99% of cases. The molecular basis of such skewed inheritance ratios is starting to be unravelled with the identification of a protein central to the process.

The cell cycle consists of four phases: S phase (in which genetic material is duplicated); mitosis (during which it is segregated between two daughter cells); and two 'rest' phases, G1 and G2. The transition between mitosis and G1 needs to be precisely timed, and one of the molecular steps involved in controlling this transition has now been pinned down to a protein known as Cdc20.

Transposons are mobile chunks of DNA that insert themselves at random in the genome. This is dangerous, particularly in germline DNA (which is passed on to offspring). A new mechanism for suppressing transposon activity in the nematode worm Caenorhabditis elegans is proposed, and it involves the until-now mysterious phenomenon of RNA interference.

The nature of the glass transition is a long-standing problem in condensed-matter science. New work shows that the motion of a small atomic species through a bulk metallic glass is due to two diffusion processes -- one that dominates below the transition and one that dominates above it.

A selection of words and images from the first issue ofNature, published on 4 November 1869.

One area of business that has been untouched by microtechnology is the textile trade. Daedalus reckons they need a micro-loom to create silicon chain mail. Such chain mail would be amazingly tough and snag-resistant, yet soft and flexible at the same time.

Most major animal groups appear suddenly in the fossil record 550 million years ago, but vertebrates have been absent from this ‘Big Bang’ of life. Two fish-like animals from Early Cambrian rocks now fill this gap.

Ingenious computational comparisons involving complete genomic sequences have predicted many new functional links between proteins, without relying on homologies to characterized proteins. These new methods complement the large-scale experimental determination of protein function, and will ultimately contribute to complete and powerful models of biological pathways and assemblies.

The control of complex cellular events relies on precise regulation of signalling molecules. The activity of many such proteins is controlled by adding a phosphate group to certain amino acids such as tyrosine, serine and threonine. A well-known motif -- the SH2 domain -- binds to phosphotyrosine residues. And a new family of proteins that bind phosphoserine and phosphothreonine is now emerging.

Careful experiments have revealed that the laws of nature (or at least elementary particles called kaons) can distinguish between past and future. Numerical calculations based on the Standard Model of particle physics now predict different results for such experiments. Is this a hint of physics beyond the Standard Model?

Proteins destined to act outside the confines of the cell need to be able to resist oxidizing processes that might unfold and destroy them. To do this they contain covalent (disulphide) bonds between cysteine residues. A huge step in understanding how these bonds are formed now comes with the first observation that protein disulphide isomerases form a direct link with partly made proteins in the endoplasmic reticulum.

During the 1990s evidence has emerged from seismic data that the Earth's inner core may be rotating slightly faster than the mantle and crust. Estimates of the rate have been as high as 3° per year. The conclusion of the latest study, however, is that there is no, or very little, differential rotation.

The formation of the outer Milky Way is still something of a mystery. Evidence that a clump of stars discovered in the outer halo and the brightest globular cluster in the Milky Way are both remnants of satellite galaxies captured by our Galaxy, may provide an answer.

One way to counter global warming would be to increase cloud cover, and so reduce the amount of solar radiation reaching Earth. Daedalus plans to do this with a save-the-planet diesel fuel which emits huge numbers of particles to act as cloud-condensation nuclei. The downside, in cold, humid conditions, will be appalling fog on the motorways.