Our body has 46 chromosomes, half that we inherited from our mothers and half from our fathers. Each chromosome has a long arm (referred to as "q") and a short arm (referred to as "p"). Each chromosome contains thousands of genes, each of which provides our body with the information it needs to grow, develop, and function properly.

The NRXN1 gene is located on the short arm of chromosome 2, at a particular location (called a "band") with the address of 16.3. Hence, the deletion is called 2p16.3 (pronounced "two P one six point three").

NRXN1 is one of the largest genes in the human genome so deletions that occur within the gene can be rather large, but still affect just the single NRXN1 gene. Therefore, NRXN1-related disorder and 2p16.3 deletion are actually the same condition.

Individuals with NRXN1 Deletion Syndrome have a deletion on just one copy of their NRXN1 gene; the other one functions normally. The size of the deletion will be different for each person but often results in the same outcome: one non-working copy of the gene. Depending on where the deletion is located within the gene, it is possible that some of the gene might still be able to function. Scientists still don't fully understand exactly how the size or location of the deletion contributes to a person's observable symptoms. We need more research to figure this out.

NRXN1 deletions can be inherited from one parent, or they can occur spontaneously in the child; the latter situation is referred to as being "de novo." Often, the deletion is inherited from a parent who had no idea they carried it. Sometimes, the parent with NRXN1 deletion has much milder or barely noticeable symptoms.