DNA forensics and the FBI

Article Abstract:

A new technique called DNA fingerprinting is being used in forensic laboratories. DNA (deoxyribose nucleic acid) is the genetic information which codes for the molecules involved in the processes of life. The DNA of an individual, like a fingerprint, is unique to that individual. DNA fingerprinting methods use restriction-fragment length polymorphism (RFLPs). RFLPs are based on mutations or changes in the DNA of an individual which allow an enzyme, or protein, to cut or not to cut the DNA in specific sites, resulting in different size fragments of DNA from every individual. The DNA which is most frequently examined is called minisatellite DNA which consists of DNA fragments that are repeated many times, in many areas of the genome (a complete set of the chromosomes which contain DNA). The number of repeats and the RFLPs present in the minisatellites vary greatly among individuals. However, not all scientists feel that the minisatellites are the best DNA to examine. Some scientists associated with the FBI (the Federal Bureau of Investigation) feel that DNA that varies in length but is present in the genome only once is a better sample to examine. Another new research method, the polymerase chain reaction (PCR), can increase the amount of DNA in a given sample so that there is enough material for testing. Standards and controls for DNA fingerprinting must be set up so that all laboratories are using the same techniques. The techniques must be sensitive (make positive identifications) and specific (rule out identifications). DNA fingerprinting techniques must also be suitable for forensic medicine, where samples are often contaminated with chemicals or other biological substances. Statistical methods which take into account the limitations of the techniques must be developed. With appropriate techniques and standards, the use of DNA fingerprinting can provide positive identification of a criminal and rule out individuals not involved in a crime.

Standards, Research, Methods, Criminal investigation, United States. Federal Bureau of Investigation, column, Forensic DNA testing, United States. Office of Technology Assessment, Forensic biology

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Cuckoos beg the answer

Article Abstract:

Cuckoos are brood parasites, laying their eggs in the nests of other birds and relying on the surrogate parents to rear their offspring. A new study of reed warblers identifies why the host species tolerate the cuckoo interlopers, which are many times their size. The research tests whether large size will stimulate high provisioning rates and shows that the single call of a hungry cuckoo chick matches that of an average reed warbler brood. It is concluded that vocal trickery, rather than large size, is the likely explanation for exploitation.

Parasitic birds, Cuckoos

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Monkey business in the aquarium

Article Abstract:

A paper based on a manuscript drafted by Konrad Lorenz in 1979 has been completed by Kurt Kotrschal and Keiko Okawa. Lorenz was interested in the vivid colours of reef fish and proposed that the colours acted as signalling posters in acquiring and defending territory. There were other arguments that the patterns may be involved in species recognition and mate choice. Lorenz studied the behaviour of reef fish in Hawaii, and built a large reef tank at his home where he studied the Indo-Pacific coral-reef fish Zanclus cornutus, or Moorish idol.

Fishes

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