Yes - 23and me! So it's not accurate then. I looked it up and nothing stood out as "Italian" for R1a. Plus nearly 30% is undetermined and everyone remotely related to me is Greek - 179 matches - all Greek. Do you recommend another DNA company? My family is planning on ordering this week from 23andme because they want to see if it shows the same Italian conclusion.
23andme is, in my opinion, while not perfect, the best testing company out there for this kind of thing. It just requires that you put some time into understanding human genetic inheritance and the way their program works.
First of all, as a woman, you don't inherit only from your paternal side. You have 22 chromosomes plus your two XX chromosomes. You inherit from both your parents on the 22 chromosomes. As for the two X chromosomes, you get one from your mother, and one from your father (by way of his mother). Your brother, if you have one, would similarly have 22 chromosomes, which would contain genetic material from both of your parents. In his case, instead of having two X's, he would have an X from your mother, and a Y from your father. That Y chromosome is what makes him male.
When your results are computed, he will therefore get a result for his y dna which you did not. Of course, the y dna chromosome is only one out of 24, and the y also contains less material than the others, so it doesn't constitute a very big percentage of his total dna.
However, you both receive, if you have the same biological mother, the same mt dna from her.
All of this is explained at their site. Search for the Facts page. That will also explain the methodology which they use to arrive at the population designation.
Their algorithm shows that certain West Eurasian nation states form discrete clusters, but some do not. Iberians will come out as mostly Iberian, Italians as mostly Italian, British Isles people as mostly British Isles. However, to my knowledge, there isn't a discrete cluster for Poles, for example. The cluster is wider and has been labeled "East European". In the case of Greeks, from what I have seen, there is no discrete Greek cluster. The cluster that forms is a broader Balkans cluster. Most people from the Balkans seem to fall into that cluster, with other minor components. From what I have read over at 23andme, some Greeks show as mainly Balkan with minority Italian, and some Greeks get a larger percentage of Italian. I don't know if the results vary by geography. There was some talk that island Greeks showed more Italian, but I don't know if that's the case. One poster also mentioned that he came from an area of Greece that had been under Italian control for hundreds of years.
I think your best bet is to use the search engine at 23andme, and also to ask for fellow Greek testees to contact you so that you can compare results. Then, you can tell if your results seem typical for your area.
As to the y-dna, I'm not sure I quite understand. Was it your brother who tested and got the R1a1a...result? I assume that's the case since you say your father is testing now. The sub-clades of R1a1a are definitely present in Greece. I've seen it attributed to the Slavic invasions, but I also think there are different varieties present there and in southern Italy nearby. Your best bet is to check the search engine here for threads about it, and you could also go to FTDNA. They have groups there that do detailed research into the y dna subclades. Unfortunatley, I don't think 23andme results are sufficient. Your brother or father would have to specifically have his y dna tested.
Hope that helps.