Genetics
For a person to have EvC they must have 2 EvC genes which they will have got from their parents. People with 1 EvC gene look normal and are called carriers. If you and your partner are carriers then you have a 1 in 4 chance (25%) of any future children having EvC (nn), a 50% chance of them being carriers (Nn), and a 25% chance of them not having the EvC gene at all (NN).
To work out the probability of prospects for your child's children in future, you can do little tables like this (See below) depending on whether their future partner has EvC, is a carrier, or is not a carrier. Since the vast majority of the population are non-carriers, the end table is the most likely scenario - no kids with EvC.
|
Both parents have EvC |
1 parent has EvC, other is carrier |
1 parent has EvC, other is non-carrier |
|||||||||
|
|
n |
n |
All children will have EvC
|
|
N |
n |
50% EvC, 50% carriers |
|
N |
N |
All kids will be carriers, no kids with EvC |
|
n |
nn |
nn |
n |
Nn |
nn |
n |
Nn |
Nn |
|||
|
n |
nn |
nn |
n |
Nn |
nn |
n |
Nn |
Nn |
|||
For the scientific among you who like getting into the nitty gritty like gene location and DNA sequences, check out OMIM. This is the medical genetics bible online!
The information above is a simplification of the inheritance of EvC. It is an autosomal recessive condition, and they have found not one, but two EvC genes, but not everyone with EvC shows abnormalities in these genes. The research continues......
How Rare Is It?
Hard to say! In all my internet research I have come across figures of 5:1000 live births in the Amish community, Lancaster County, Pennsylvania due to one of its founders Samuel King. The same report said that there were 1:60,000 births throughout the U.S., but these results may be skewed slightly due to the Amish community. Another report I read, European this time, quoted 1:150,000 births. I even asked Angus' consultant geneticist, but she said that it would be hard to say since EvC is rare but under-reported. The most likely figure for the UK is 1:200,000 live births which equates to about 3 children a year. I got this figure from Michael Wright who is researching EvC in Newcastle, but even he says this is an estimate and there are no hard data to back this figure up.