DNA Testing for genealogy

[PaulineJ]

I'll try to remember for next time.    Pauline

[paulalou]

I've been reading this topic with interest as i'm a geneticist. The ethics around genetic testing is a debate that can go on for ages. I personally would be interested for myself from a genealogical level especially as i think my grandfathers parents were first cousins and haven't been able to confirm this from the usual sources...although there are some big hints.

[criggy]

Funny how things skip a generation. My son doesn't particularly look like either me or my husband but when it was my dad's 80th we compiled a wall chart of dad through the ages. He and my son were married at a similar age and there is a striking similarity between them - everyone commented about it.

Now perhaps my dad and his grandfather looked similar and dad's grandfather and his grandfather etc

The mind boggles...

[Geoff of Devon]

Paul,
I noticed in my tree that several cousins inter-married, BUT only had children if they were three generations between their common ancestor. My family was obsessed in keeping their wealth. At least, up until about WW1!
I remember from reading a book about Eleanor of Acquitaine that there was a catholic rule, that could only be overuled by papal intervention, that stipulated this.
What are the exact genetic effects upon say immunity?   I know they quote Queen Victoria and the general Sax-Coburg line and their genetic diseases as the most common example.
Geoff.

[paulalou]

Geoff,

By inter-marrying any rare mutation that could be disease-causing is more likely to be seen in the offspring. For example, in some diseases you need two copies of the defective gene for a disease/disorder to occur (one from each parent). In the general population you may never find anyone else carrying the defective gene (assuming having one copy of the defective gene and one normal copy = a normal person). But within a family the chances of two people each carrying the defective gene is higher therefore the chances of their offspring have two copies is also higher. Of course there are always exceptions to the rule.

Paula