DNA solves a family mystery...sort of

My grandfather said his father always insisted that that ’Gus’ wasn’t short for anything. He was Gus — not Angus, August, Augustus or anything else.

The records at Ellis Island say something different. Before 1918, they show a sailor named Gustav Crenson sailing into New York City on three occasions. But on three occasions after that it’s just Gus, or simply “G. Crenson.”

In an era when sauerkraut was being referred to as “liberty cabbage,” perhaps Gus was trying to avoid drawing attention to a Teutonic pedigree.

He also had an odd way of pronouncing some words, my grandfather reports — like “veel” for “wheel.” And the affidavit says that his parents’ names were Martha ... and Otto.

Could my great grandfather have been German?

The answer could be in my own DNA.

Most of our genetic material gets passed from one generation to the next through a process known as recombination. Recombination keeps us from being clones by giving everyone (except identical twins) a unique combination of genes, half from each parent.

That mixing process makes most of our DNA practically useless for inferring ancestry, at least with current technology. But there are two small sections of the genetic code that never recombine. The Y-chromosome, which confers maleness, is passed directly from fathers to their sons. Another odd little package of genes known as mitochondrial DNA is always inherited from the mother.

Those two portions of DNA can only change by mutation. That means if you know how fast the genes of the Y-chromosome or mitochondrial DNA mutate over the generations, you can calculate how long ago two people shared a common ancestor by comparing their genetic code.

Mitochondrial DNA mutates relatively slowly. So it is hard to use it to find out about what happened in the last few generations, or even in historical times. It is better-suited to studying the expansion of the human species out of Africa 70,000 years ago, the arrival of people in the Americas more than 12,000 years ago or the spread of agriculture into Europe after the ice age.

But the Y-chromosome mutates faster, making it practical for exploring genealogical relationships in the last few hundred years. That was exactly what I needed.

I contacted a genetic testing organization, Family Tree DNA, based in Houston. I scraped my cheek with a little brush, dropped it into a preservative solution and sent it off.

Then I waited as the company extracted the DNA from my spit sample and created a genetic profile of it. The procedure is very similar to forensic DNA fingerprinting, which looks at multiple sites where the genetic code can vary from one person to another. Look at enough sites, and the particular combination of variants in any given person is virtually unique.

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