Understanding how the genes you inherit may influence your health
The genes you inherit from your parents programme your development from a single fertilized cell at the moment of conception to adulthood. Humans have about 20,000–25,000 pairs of genes arranged on 23 pairs of chromosomes. One chromosome from each pair is inherited from your mother, the other from your father. The mix of genes is slightly different in each sibling.
Genes control the metabolism, growth, repair, and reproduction of cells. They are responsible for the development of the embryo, first into a baby, then a child, and eventually an adult. Throughout your life, genes control cell functions and the repair and replacement of dead or damaged cells.
Blood relatives have many genes in common, and these genes help to determine family physical characteristics and other traits. Many of these traits, such as the shape of the nose, have no significance for your health. Other traits, such as being unusually tall or short or having a tendency to be overweight, can be associated with an increased risk of certain diseases.
Some diseases, such as haemophilia and cystic fibrosis, are directly caused by a fault or mutation in a single gene or pair of genes. These rare diseases follow a predictable pattern of inheritance, and this means that families in which the altered gene is present can usually be given clear, reliable information regarding the probability of the disease affecting future generations.
More common than these genetic disorders are those in which genes, along with other factors, contribute to a family’s susceptibility to certain diseases. For example, some disorders, such as coronary artery disease, tend to run in families, but lifestyle factors such as a high-fat diet, smoking, and lack of exercise also play a part in determining whether these diseases develop.
In some diseases that have a genetic component, including asthma, environmental factors, such as living in a polluted area, also play a crucial role.
The complex interplay between genetic susceptibility and environment makes it difficult to predict the risks in adult life for children who are born into families affected by disorders of this kind.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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