DNA test

[Marianne]

In case I want to trace my ancestry what kind of DNA test do I need to do since Im female and I dont have Y-chromosome?
I suppose I could ask my brother to have a DNA test but what happens if a girl's brother isnt her biological one? Also what about the the ancestry from the mother's side of a person when there are no living male relatives of the mother?
For example, I have a friend whose father is Greek and mother is from Finland and they live in Greece. Assuming his Y-chromosome haplotype is J2 (high chance since his father is Greek), if he didnt know his biological parents and decided to do an ancestry DNA test he would never have a chance to learn that he is half from Finland and he carries finnish genes since mdna test is not that accurate, right?

If this is true, the currenct ancestry testing sounds really incomplete to me (excludes half of the genes a person is carrying) making all those lists with the haplotype frequency in each country very inaccurate and all the countries a lot less homogenous than what we see at the moment. Especially if we consider that a man was very likely to have kids with different women, also enslaved ones from asian/african countries, in the past, therefore producing male descendants, whose mothers' ancestry doesn't appear in the current DNA tests, a notable percent of the european population at the moment is very likely to carry non European genes that we can't trace and add to the lists of ethnicities in European countries (at least that's how it sounds to me).

[Maciamo]

Marianne,

If your purpose is to have your "ancestry painting", for example if you think you might have non-Greek ancestrors but aren't sure about it, the test you should take is an autosomal DNA test, such as the one offered by 23andme. This is currently the best value test because it tests a bit of each chromosome + mitochondrial DNA. What you will get is :

- your mtDNA haplogroup (+Y-DNA for men)
- ancestry painting showing where you stand on a virtual map of Europe (so if you are half Greek and half Finn, to use your example, you will be half-way between Finns and Greeks).
- your health profile, including risks for various genetic diseases, but also informative traits. You can see a non-exhaustive list of mutations tested by 23andMe in the genetic section.
- you can also compare the percentage of similarity for selected traits with your family and friends (or anybody you choose to share your data with).
- you can compare family inheritance of chromosome sections. If you have a doubt about your brother being your brother, for instance, you can be sure by comparing this.


The main interest of Y-DNA tests is not to know one's detailed ancestry (it's only one line out of millions), but rather to understand better historical migrations and the overall composition of a targeted population. It's interesting to know which ancient ethnic groups merged to make the present population of a country or region. Inside Greece, if your ancestors all come from one specific region, you can know that the genetic make-up of that region is quite different from another region. For instance Crete has a lot of J2 and little R1a, while it is the opposite in Macedonia.

[Marianne]

I didn't know about this test. It's very interesting and sounds good value for the money they charge.

One more question. If a person has phenotype characteristics caused by dominant genes and the parents don't have those characteristics, does that mean that they are for sure not the biological ones?
Are there lists of characteristics proven to be due to dominant or recessive genes? For example, I know from the biology classes I had in middle and high school that attached earlobes, thalassemia and hemophilia are due to recessive genes but pointed chin, the ability to fold the tongue, brown eyes etc are due to dominant genes.

[Maciamo]

I didn't know about this test. It's very interesting and sounds good value for the money they charge.

One more question. If a person has phenotype characteristics caused by dominant genes and the parents don't have those characteristics, does that mean that they are for sure not the biological ones?
Are there lists of characteristics proven to be due to dominant or recessive genes? For example, I know from the biology classes I had in middle and high school that attached earlobes, thalassemia and hemophilia are due to recessive genes but pointed chin, the ability to fold the tongue, brown eyes etc are due to dominant genes.

No, it's the opposite. If both of your parents have traits caused by recessive genes (not dominant ones) you will have this trait too. If you don't there is a high chance that either or both parents isn't yours (the only alternative is that the trait isn't really recessive or involves many mutations).

So if both your parents have attached earlobes and blue eyes, you should have attached earlobes and blue eyes too.

With dominant traits, only one allele is required, so we cannot know if a person has one or two dominant alleles without a DNA test. A European with brown eyes could very well have one allele for brown and one for blue. If both parents have one of each, both parents will have brown eyes but children can have either brown or blue eyes.

Actually eye colour is complex and involved many mutations (over 30 in the OCA2 gene). That's why some people can have mixed colours (brown with some green, or blue with some yellow/brown).

[Marianne]

What I meant was, if someone lets say has the ability to fold the tongue (dominant) and the parents don't have it (they have the recessive gene) that means that they are not the biological ones? Cause if one of them was carrying the gene to pass it to the child (that has it) he/she should have the phenotype also, right?

I mean if the recessive gene is f and the dominant is F, both parents will be ff, ff and they have no chance to pass the F to the child which will be either FF or Ff (since it has the characteristic)

[Maciamo]

What I meant was, if someone lets say has the ability to fold the tongue (dominant) and the parents don't have it (they have the recessive gene) that means that they are not the biological ones? Cause if one of them was carrying the gene to pass it to the child (that has it) he/she should have the phenotype also, right?

I mean if the recessive gene is f and the dominant is F, both parents will be ff, ff and they have no chance to pass the F to the child which will be either FF or Ff (since it has the characteristic)

Theoretically you are correct. But I don't think that the ability to fold one's tongue is 100% genetically determined. Practice may have a role too. I googled it and it seems that the genetics of tongue curling is complex and uncertain at this point.

Blood type would be a more obvious choice for comparison. You can't always know, but if both your parents are O (recessive) then you must be O. If one parent is O and the other is A, you cannot be B or AB. Have a look at the inheritance chart. This is completely reliable.

There are many other blood types than ABO, and some are tested by 23andMe (Diego, Kell, Kidd, Duffy). The blood type card that you can get by doing a simple blood test at your doctor's usually has at least ABO and Rhesus.

[Marianne]

Yes I also assume it's a lot more complex with many characteristics, especially those that are not determined by only one pair of genes. For example I read that it is possible for 2 parents with blue eyes to have a biological brown eyed child (although rare).

I guess if someone wants to be sure about the parents, DNA test is the way to go.