Personally I believe that this whole chapter is symbolic. I could never understand why the number 144,000 was literal and then the description of those ones was symbolic. I asked many people when I was a witness and even elders and those who professed to be "anointed" and no one could come up with a satisfying answer. My reason for coming to this conclusion is as follows:
The description is symbolic so therefore it would make sense that the number is also. The numbers are used in the bible as representative of something else. The number 12 meaning completeness. There are 12 Apostles and the number 12 (completeness) can be divided into 144,000 exactly 12,000 times.
Also, I could never understand how the true church (or body of Christ) could only be made up of 144,000 faithful for two reasons:
1 - The bible says as many as recieved him (Jesus) he gave authority to become sons of God. It does not say until the 144,000 is completed.
2 - If you look back into the past, there have been tens of thousands of diciples of Christ put to death as martyrs. These include those thrown to lions, burned alive, tortured and killed by the catholics, etc.
I find it interesting also that nowhere in Revelation does it equate the number 144,000 with those who sit on thrones or rule the earth. But about the great crowd (who the witnesses teach are earthly) it says they were chosen to sit on thrones. Rev. 5:9,10. Also, Rev. 7 says that the great multitude (or crowd) was in heaven.
As someone pointed out, Revelation is a very symbolic book and should not be taken literally or the beast would be an actualy beast and the dragon an actual dragon! This is only my two cents worth.
In light of what I think may be true that it is not literal, the virgins could be in a spiritual sense. Another side of the coin is that some believe that a literal number of 144,000 male, virgins will be sealed for deliverance during some time in the end. I am only adding this to show there are different views but I think we shall just have to wait and see. Lilly