And I heard the number of them that were sealed, a hundred and forty and four thousand, sealed out of every tribe of the children of Israel: (ASV)
The next four verses go on to list the 12 tribes of Israel as:
Judah, Ruben, Gad, Asher, Naphtali, Manasseh, Simeon, Levi, Issachar, Zebulon, Joseph, Benjamen.
If one choses the twelve tribes are to be descendants of the sons of Jacob, then the above list leaves out Dan. Mannasseh was a son of Joseph.
If one choses the twelve tribes to be those granted a parcel of land by God, then the above list leaves out Dan and Ephraim. Ephraim was another son of Joseph. Levi's descendants were preists and could live anywhere. Joseph's descendants were given a double share, one for Ephraim and another for Manasseh, since Joseph saved the family for starvation by providing for them in Egypt.
The tribe of Dan had become idolators and were therefore left out of the list of tribes to be replaced by the tribe of Ephraim that is frequently in the OT referred to as the tribe of Joseph.
Edit this section to note miscellaneous facts.