How do I know if I have the inherited form of kallmann's syndrome?

Almost all people who have inherited Kallmann's syndrome are male. If your brother, father or grandfather also has or had Kallmann's syndrome, then you almost certainly have acquired the disease by inheriting the defective Kallmann gene from one of your parents, most probably your mother. To understand how Kallmann's syndrome could be passed on from generation to generation, we must first understand the basic principles of genetics.

You may have already heard of or read about DNA fingerprinting and genetic engineering, but probably wondered what these terms actually mean. Much of your body is made up of thousands of millions of microscopic cells, all of which have a central nucleus, each containing tiny thread-like "packages" of information known as chromosomes (see Figure 15a). Chromosomes are made up of even smaller units called genes containing copies of a code describing every one of our physical characteristics and features, such as the colour of our skin, hair and eyes and even the likelihood of us developing particular diseases. Each one of these genes consists of a specific segment or sequence of the highly complex "building block" of life, the DNA molecule. Each one of your cells (except your sperm or egg cells) has an exact copy of 23 pairs of chromosomes and unless you have an identical twin, your genetic code is unique to you. This forms the basis of "DNA fingerprinting" and "genetic engineering" which are used, amongst other things, for catching criminals. Samples of blood, saliva, semen or hair, all of which contain DNA, can be taken from a crime scene and these can then be used to confirm that a particular suspect was present at the scene.

One of the 23 chromosome pairs is the pair of sex chromosomes. As the name suggests, the sex chromosomes determine a person's sex. A male has one X and one Y sex chromosome and the female, two X chromosomes. The remaining 22 pairs of chromosomes are known as the autosomes. Only sperm or egg cells have less than 23 pairs of chromosomes; they have exactly half this number or 23 unpaired chromosomes (see Figure 15b). This is because when an egg is fertilised by a single sperm cell, both parents' genes are brought together and the total number of pairs of chromosomes in the fertilised egg cell adds up to the usual 23.

The most widely studied form of inheritance: X-Linked Kallmann's syndrome

Except in very unusual circumstances, the mother's unfertilised egg cell always has one X sex chromosome, whereas the father's sperm cell can either have an X or a Y sex chromosome. When the egg cell is fertilised by the sperm cell, the sex of the baby is established, XY for boys and XX for girls.

Occasionally, an abnormal gene is inherited from one of the parents. In inherited Kallmann's syndrome, the abnormal or Kallmann gene is located on the "X" sex chromosome (Figure 16a). The Kallmann gene is therefore defined as being X-linked. If a male, who always gets his single read more