Genesis was most likely written after Deuteronomy. The list of patriarchs Noah back to Adam is extended by two names from the earlier Sumerian writtings about a great flood.
About the time of Berrous is when this seemed to happen and Howthebiblewascreated had mentioned to me is was also at this time that the demensions of the ark in the Genesis story become what they are today, for earlier stories make the ark many different sizes but nothing like the Ark of Genesis.
One has to remember that the Bible writtings have many instances where the writers took writtings from other sources to put into the Bible.
Proverbs has connections to Ugarit and the writings of Amenope. Some of the psalms can be connected to Ugarit as well as parts of Daniel.
The passover festival could possibly be connected to Ugarit. Genesis has similarities to that of the Enuma Elish and theres a bunch of stories from Ugarit and Sumeria that found there way into the Bible.