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Thursday, July 2, 2015
Inherited Disorders and Birth Defects
Syndactyly and mating
Is Syndactyly a common occurance with inbreeding?
No, not necessarily. Syndactyly or webbing of the fingers and toes is a very common finding which can be a normal variation or minor anomaly. Syndactyly can be sporadic - that is, it happened just in one child in a family, is not inherited from either parent and geneticists do not know why it happened. It can also run in families – where a parent has a gene that codes for syndactyly and can pass that gene on to any of his or her children. Finally, syndactyly can also be seen in many genetic disorders, but these children have multiple problems, not just syndactyly.
Syndactyly often is inherited in as an autosomal dominant trait. For all of our genes – there are 2 copies of each. Autosomal dominant inheritance describes a trait or disorder in someone who has a gene mutation (or change) in one of the two copies for that specific gene.
Anyone with an autosomal dominant inherited trait or disorder has a 50-50 chance of passing that gene on to any child that person has. Autosomal dominant traits can be seen in both males and females equally. Usually, when someone has this gene mutation for a trait, such as syndactyly, you see it in multiple generations. However, some genes are not 100% penetrant. Penetrance is the proportion of people with a gene mutation causing a particular trait or disorder who actually show the trait. So in some families, if the gene is not 100% penetrant, if may look like it has "skipped" a generation.
Syndactyly is not a sign of inbreeding. However, if there are family members who are related, there may be an increased chance that a gene that codes for syndactyly will be seen more frequently in that family.
Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University