Jewish Genetic Disorders
What is a genetic disorder?
A genetic disorder is a condition caused by an abnormality in an individual’s DNA.
What are Jewish genetic disorders (JGDs)?
These are genetic disorders which are more common in people who have Jewish ancestry than those in the general population.
This does not mean that only Jewish people are affected, but it does mean that Jewish people, or those of Jewish descent, have an increased risk of having one of these conditions.
Why are certain disorders more common among Jewish people?
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.
Do Jewish genetic disorders affect Ashkenazi, Sephardi and Mizrahi Jews?
Yes. People often assume that this phenomenon only applies to Ashkenazi Jews. However, JGDs impact Sephardi and Mizrahi Jews too.
Different disorders impact these different groups. Also, unlike the ‘Ashkenazi JGDs’, Sephardi and Mizrahi JGDs are linked to country of origin. For example, Iranian Jews are at risk of carrying different JGDs to Iraqi Jews, and again to Yemenite Jews. There are some JGDs that are relevant to more than one Sephardi sub-group, and some that are relevant to both Ashkenazi and Sephardi Jews.
The Jnetics carrier screening test covers 47 recessive JGDs, including a variety of severe Ashkenazi, Sephardi and Mizrahi disorders.
How are Jewish genetic disorders inherited?
Genetic disorders can be passed to the next generation via autosomal dominant, autosomal recessive or X-linked inheritance.
How common are Jewish genetic disorders?
The majority of these conditions are rare. However, it is not uncommon for people to be a ‘carrier’ for one or more disorders and therefore at increased risk of having an affected child.
Some dominant Jewish genetic disorders are common. The Jewish population have a significantly increased risk over the general population of carrying a BRCA mutation, which puts them at increased risk of certain types of cancer. You can find more information about BRCA associated cancer here.
Autosomal dominant inheritance occurs when an alteration in just one copy of an inherited gene pair causes a genetic disorder.
Autosomal recessive inheritance occurs when alterations in both copies of an inherited gene pair are required to cause a genetic disorder.
Introduction to Genetics
Genetics is the scientific study of inheritance, or how particular qualities, traits, or genes are transmitted from parents to their children.
Basic concepts in genetics:
Genes are the basic units of inheritance. Genes are made of a chemical called deoxyribonucleic acid, commonly referred to as DNA.
Each gene contains instructions for making a specific protein, and each protein has a particular characteristic or function in the body. This means that genes determine certain features e.g. eye colour, or instruct the body to make a certain enzyme.
Genes are packaged into structures called chromosomes that are found in the nucleus of every human cell. A normal human cell contains 23 pairs of chromosomes.
Each parent contributes one chromosome to each pair so that individuals get half of their chromosomes from their mother and half from their father.
A mutation/variant refers to a structural change in a gene. It can be an alteration to a gene’s size, arrangement, or molecular sequence.
Genetic disorders can arise when one or both copies of a specific gene have undergone a mutation/variation.