the 12 tribes of Israel...

In the Bible, the 12 tribes of Israel are talked about a few times... in Exodus, Numbers and in Revelation. I don't know about anyone else but when I read in the bible that the 144,000 elect that govern the kingdom with Christ are 12,000 from the 12 tribes of Israel, I take that literally. Revelation 7:4-8 -
⁴ Then I heard the number of those who were sealed: 144,000 from all the tribes of Israel. ⁵ From the tribe of Judah 12,000 were sealed, from the tribe of Reuben 12,000, from the tribe of Gad 12,000, ⁶ from the tribe of Asher 12,000, from the tribe of Naphtali 12,000, from the tribe of Manasseh 12,000, ⁷ from the tribe of Simeon 12,000, from the tribe of Levi 12,000, from the tribe of Issachar 12,000, ⁸ from the tribe of Zebulun 12,000, from the tribe of Joseph 12,000, from the tribe of Benjamin 12,000.

The last visit that I had with the JWs talked about this very topic. They believe (from what I understand) that the 144,000 are JWs that God has chosen already. They say that the tribes named in Revelation are different from the ones in Genesis and that people who are believers are adopted Israelites. (although, it would seem from scriptures that they have pointed out to me, that they do not think that I am a true believer, which really gets on my nerves.)I told them that I believed that two tribes had been replaced and I couldn't find the reference for it so I did some digging after they left.

In Revelation the tribes listed are:

Judah, Reuben, Gad, Asher, Naphtali, Manasseh, Simeon, Levi, Issachar, Zebulun, Joseph and Benjamin.

In Genesis, Exodus and Numbers, they are:

Judah, Reuben, Gad, Asher, Naphtali, Manasseh, Simeon, Issachar, Zebulun, Ephraim, Benjamin and Dan

I wanted to find out why they were different. So I googled. I found a website that seemed to answer my question... Why were Ephraim and Dan left out of Revelation? Well, we aren't always going to really understand the ways of God but there are a few interesting ideas floating about... In Genesis, Jacob gives his blessings to his sons when he is dying and of Dan he says,

Dan will be a snake by the roadside, a viper along the path, that bites the horse’s heels so that its rider tumbles backward.

In Hosea it is written:
Ephraim will be laid waste on the day of reckoning. Among the tribes of Israel I proclaim what is certain... Ephraim is oppressed, trampled in judgment, intent on pursuing idols.

In Psalms the men of Ephraim did not keep their covenant with God and refused to live by his law. Even though God freed their ancestors from Egypt they rebelled against Him!

Could this explain why Dan and Ephraim are not a part of the 12 tribes in Revelation? Only God knows for sure...