Polydactyly is an inherited condition in which a person has extra fingers or toes. It is caused by a dominant allele of a gene. This means it can be passed on by just one allele from one parent if they have the disorder.

Syndromic polydactyly The syndromes are thought to be caused by genetic mutations that affect the signaling pathways during an embryo’s development. Limb malformations are often associated with problems in other organs.

So why if there are many dominant versions of genes that make six fingers is having six fingers rare? Well, those versions of genes are rare. You don’t meet many people with extra fingers or toes. This means when two people meet and have a baby, odds are neither has the “six-finger” copy of a gene.

Although it affects many species, it’s still pretty rare—even though much of the time, having six fingers is actually controlled by a dominant allele. An allele, or version of a gene, is dominant when it only needs to be present in one copy in your cells for its associated traits to be discernible.

The vast majority of occurrences of polydactyly are sporadic, meaning that the condition occurs without an apparent cause — while some may be due to a genetic defect or underlying hereditary syndrome. African-Americans are more likely to inherit the condition than other ethnic groups.

Diagnostic tests include amniocentesis or chorionic villus sampling. Your provider also can check your baby’s blood for chromosomal conditions after he’s born.

The most common birth defects are:

• heart defects.
• cleft lip/palate.
• Down syndrome.
• spina bifida.

Clinodactyly is a congenital condition. That means a child’s born with it, as opposed to developing it later on. The unusual shape may be caused by the growth of an abnormally shaped finger bone or by a problem with a growth plate in one of the finger’s bones.

The exact incidence of this condition is unknown, in part because there is no precise definition of what level of curvature is normal and abnormal. It tends to be present more commonly in boys and usually affects the small finger; it is unusual to have it on both hands.

Bent Little Finger (L): A dominant allele results in the end joint of the little finger of each hand bending inward. Straight little fingers are a result of the recessive genotype.

Camptodactyly is a rare condition where a finger — or fingers — is fixed in a bent position at the middle joint, and cannot fully straighten. Affecting less than 1 percent of the population, camptodactyly is most often found in the pinky finger and can occur in one or both hands.

Clinodactyly is a medical term describing the curvature of a digit (a finger or toe) in the plane of the palm, most commonly the fifth finger (the “little finger”) towards the adjacent fourth finger (the “ring finger”).

Interlocking fingers: Clasp your hands together with your fingers interlocked. A dominant gene is probably present if your left thumb is on top of your right. If your right thumb is on top, then you have the recessive gene.

Most people place their left thumb on top of their right and this happens to be the dominant phenotype.

Holding hands while interlocking fingers denotes an innate closeness. When a couple holds hands with their fingers entwined and palms facing forward, that’s a sign they have “a very intimate connection,” body language expert Traci Brown told Elite Daily.

Describing a trait as dominant does not mean it is the most common; it means that it is expressed over the recessive trait. For example, tongue rolling is a dominant trait, controlled by the dominant version of a particular gene (R). Individuals with one or two copies of R will exhibit tongue rolling.