Genetic Traits



There is some debate among researchers as to what really causes twins, triplets, and other multiple births. Although the mechanism is well understood for fraternal twins, identical twins are generally still considered to come about by chance and any occurrence in a family across generations is mere coincidence.

Dizygotic twinning, or fraternal twins, are thought to occur because there is an inherited genetic trait which causes hyper-ovulation in the mother, resulting in multiple fertilizations. This trait is then passed on to both her male and female children, although the males can only pass it on to their daughters. This might explain the anecdote that twins 'skip a generation'. A woman who is herself a fraternal twin is 2.5 times as likely to have twins as someone from the general population. A mother of fraternal twins is 3-4 times more likely to have another set of fraternal twins. A woman who is an identical twin is no more likely to have twins compared to someone else.

Scientists haven't identified and confirmed a clear cause for monozygotic twinning, or identical twins, which occurs when a fertilized egg splits and develops into two (or more) embryos. The process appears to be random chance. However, there is a study that has suggested that there is an enzyme in sperm that could cause an egg to split after fertilization. This would mean that similar to hyper-ovulation in mothers, there is an inherited trait to the father which causes eggs to split into identical twins. This trait would also appear 'skip a generation' if passed through a daughter to a grandson.

Neither of these above factors preclude twins born of random chance, they merely increase the odds. And the random element of genetic inheritance means that these traits are not expressed in every single offspring.

That said, twins certainly seem to run in our George branch of the family tree. John Wall, Ellen Wall, Orville George were each generations who bore twins. Orville's grandparents on the other side, William and Mary also bore twins. No other family branches share the same propensity for twin births.

It is not known whether these ancestors were fraternal or identical twins, but Orville George's daughters are known to be identical twins, as confirmed by a genetic test in July 2012. His wife, Diana Neilson, had no history of twins of any kind in her family line, which if we are to apply the theory described above, makes sense, as Orville could have carried the gene which would split the egg into multiple zygotes. Perhaps he inherited this trait from his grandfather Thomas Dagg, who got it from his grandfather John Wall. If true it means that Orville's male descendants might also carry this gene.

But this would still not explain why Ellen Wall, also bore twins. Perhaps it was just chance. With further research we could determine what type of twins all of these generations bore to make more sense of it.


Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease is an inherited neurological disorder that takes different forms, but is part of the Muscular Dystrophy group of diseases. It is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs but also in the hands and arms in the advanced stages of disease. Currently incurable, this disease is one of the most common inherited neurological disorders. Estimates of incidence are about 1 in 2,500 people affected worldwide. Most cases of the disease are inherited in an autosomal dominant pattern. This means that one copy of the altered gene in each cell is sufficient to cause the disorder, but will not be passed on to descendants if the altered gene is not present. Rarely, some cases of CMT disease result from a new mutation and occur in people with no history of the disorder in their family.

In our family ancestry, CMT appears to have been passed down the Dagg family line of the George family. It was inherited by a number of the descendants of Arthur George and Ethel Dagg. It is not known how far back it extends in our family.