Ask Mr Brain . . . all will be explained

PUBLISHED : Friday, 24 November, 2000, 12:00am
UPDATED : Friday, 24 November, 2000, 12:00am

Why do babies, whose parents are close relatives, more likely to be retarded?

This is probably due to the fact that close relatives share many closely similar genes. The children that they have are more than likely to inherit these genes. While this seems fine when the genes are to do with colour of hair and so on, the serious side appears when the genes carry defects.

While members of the family may be carriers of certain hereditary defects (recessive genes), when they have children with someone not a family member who does not share this gene, the defect may remain hidden. But when they have children with a family member, who is more likely to carry the same defect or weakness in the gene, the child is also more likely to inherit the defect.

Inbred children may well be normal, but there is a heightened risk of inheriting genetically related diseases such as haemophilia, and may suffer birth defects such as extra fingers or toes. In a study of Japanese children from birth to 10 years of age, a professor of human genetics found that the death rate among inbred children was 1.5 per cent higher than all other children.

Will people be attacked by thunder when they are bathing?

Actually, thunder is the sound you hear when air expands explosively as it is heated by lightning. Lightning occurs when the electrical charges in clouds rub against each other. So lightning is really electricity, and thunder is the sound that comes with it.

Water conducts electricity, so if lightning strikes water, electricity will pass through everything in the water . People can be easily hurt if they stay in or around water outdoors when there is thunder and lightning. If you are indoors however, bathing is usually safe, as most buildings have lightning conductors on the outside, and if the building is struck by lightning, the electricity will run down the conductors to the ground, leaving everyone in the building safe.

Lightning is very dangerous, because electricity can kill. Every day someone is struck by lightning. Most of them survive but many do not. In the United States, about 200 people die each year from lightning or the fires it causes. The safest thing to do in a thunderstorm is to stay indoors.