A genetic disorder is a condition that is caused by an abnormality in an individual’s DNA. Lots of different disorders are now known to be caused by this, and more are being described all the time.
These are genetic disorders which are more common in people who have Jewish ancestry than in the general population. This does not mean that only Jewish people are affected, but it does mean that people who are Jewish, or are of Jewish descent, have an increased risk of having one of these conditions.
Many years ago, Jewish communities were small and isolated, with members tending to marry within their communities. A small number of people over many, many generations can pass on a DNA abnormality within an ethnic community, even when that community is no longer small and isolated. For this reason, most ethnic groups have genetic disorders which are more common in that population than in the rest of the world.
The answer is changing all the time as new discoveries are made. At the moment, scientists and doctors have studied and identified in detail over 30 conditions which are particularly relevant to people who have Jewish ancestry. Some particularly affect those of Sephardi ancestry and some particularly affect those of Ashkenazi ancestry.
Jewish people can usually trace their origins back to either Ashkenazi or Sephardi roots, or to both. Ashkenazi Jews are at risk from a different group of genetic disorders than those affecting Sephardi Jews.
Sephardi disorders also tend to be specific to community of birth and do not affect all Sephardi Jews to the same extent. This means that disorders that are more common among Sephardi Jews from one region e.g. Tunisia tend to differ from those that are more common among Sephardi Jews from other areas e.g. Syria and Morocco.
Most Jewish genetic disorders are inherited in a recessive way. This means that both parents need to be a ‘carrier’ of the same condition in order for there to be an increased chance of their children being affected.
With recessive genetic disorders, ‘carriers’ are not themselves affected by the condition. As such, affected children can often be born to families that have no other known cases of the genetic condition among their relatives.
A few of the disorders are inherited in a dominant way. This means that only one parent needs to be a ‘carrier’ of a disorder in order for there to be an increased chance of their child being affected. With dominant conditions, the parent ‘carrier’ may or may not be themselves affected by the condition.
For a more complete explanation about inheritance see introduction to genetics.
The majority of these conditions are rare. It is not uncommon, however, for people to be a ‘carrier’ for one or more disorders.
It is estimated that everyone of Ashkenazi Jewish ancestry has a 1 in 5 chance of carrying at least one of the main Jewish genetic disorders.