Rachel Olson, a forth-former at Westland High School, asks :-

Why are some people deformed?

Ingrid Winship, a molecular biologist at the University of Auckland Medical School, responded.

Dorlands Medical Dictionary defines a deformity as "distortion of any part or general disfigurement of the body; malformation".

Inherited (genetic) causes may be chromosomal abnormalities which may arise as an extra chromosome, or a piece of chromosome extra, or missing. The commonest example of this is the Down Syndrome. Many genetic disorders are caused by a tiny fault in the DNA which makes up the chromosomes. Examples of these single-gene defects include extra or missing fingers or toes, or even whole limbs, heart defects and many so called syndromes. Some genes are dominant over others and there are many patterns of inheritance of genes; this implies that this genetic disorder may recur in the family. Multifactorial conditions such as cleft palates and club feet, are caused by an interaction of genes and the environment.

Acquired causes include the group of teratogens, one of the most important of all causes of deformity. These include chemicals, drugs, irradiation and viruses which have an adverse effect on the unborn baby. Thalidomide, a medication used in the 1940's, caused babies to be born with missing limbs. Alcohol in any amount is dangerous to the developing foetus and the Foetal Alcohol Syndrome is a well recognised cause of abnormalities in children. Rubella and the AIDS virus in pregnancy may cause major problems to the unborn child.

There are a host of other causes of "deformity" including other disorders such as diabetes in the pregnant mother, and bands of amnion tissue which may wrap around the baby and cause damage. The extent of the effect of the non-genetic causes are determined by many factors including timing, as the development of the foetus follows a strictly chronological pattern. The first 14 weeks are the most critical times.