Ask Mr Brain . . . all will be explained

PUBLISHED : Friday, 15 December, 2000, 12:00am
UPDATED : Friday, 15 December, 2000, 12:00am

Can an animal be the hybrid of two existing animals?

A hybrid is an animal or plant produced from parents of different breeds or types.

The mule is a hybrid - it is the offspring of a male donkey and a female horse. But you cannot mate two mules and get another mule, because they are sterile.

Hybridisation also takes place between coyotes and domestic dogs, most possibly because coyotes and domestic dogs are much more closely related than horses and donkeys are.

Many factors prevent hybridisation between species. Most will not mate in the first place. If they do, or if humans artificially inseminate an animal to see what kind of animal is produced, many will not produce offspring because the sperm and egg do not recognise each other. Even if offspring is produced, it may be sterile, like in the case of the mule.

Who is a 'guru'?

In Hinduism, a guru is a personal teacher or guide who has attained spiritual insight.

In the education system of ancient India, knowledge of the Vedas (sacred scriptures) was personally transmitted through oral teachings from the guru to his pupil. The pupil lived at the home of his guru and served him with obedience and devotion.

The word 'guru' has come into general use in English to denote a person who is an expert on a particular subject, for example 'technology guru'.

How do surgeons get access to the brain for surgery?

First, the skin, tissue and muscle covering the skull is cut using a scalpel and electrocautery, a technique which burns the tissue just enough to seal tiny blood vessels that may bleed.

Next the skull is opened with a variety of stainless steel tools such as chisels, drills and handsaws.

The tools are similar to those a carpenter would use, but they are built to withstand repeated sterilisation.

After surgery, the removed piece of skull can be put back, or titanium plates or pieces of bone from another part of the body can be used to replace the skull.

Another method of surgery on the brain such as to treat tumours can be done without opening the skull. A technique using a 'gamma knife' precisely focuses radiation on to a tiny target area to destroy a tumour.

When tumours are detected by medical scans, computer imaging is used to make a three-dimensional model of the tumour.

The gamma knife is then programmed to send a does of radiation to the diseased cells. The DNA in the diseased cells is destroyed and the cells are unable to multiply.