Is there a reason provided in Genesis for the enslavement of the ancient Israelites for 400 years?:

> 
> Genesis 15:13 And he said unto Abram, Know of a surety that thy seed
>  shall be a stranger in a land that is not theirs, and shall serve
>  them; and they shall afflict them four hundred years; 
> 
> 
> 

Exodus chapter 1 reports how the Pharaoh felt threatened by the ancient Israelites and enslaved them:

> 
> Exodus 1:8-11 Now there arose a new king over Egypt, who did not know
>  Joseph. And he said to his people, "Behold, the people of
>  Israel are too many and too mighty for us. Come, let us
>  deal shrewdly with them, lest they multiply, and, if war breaks out,
>  they join our enemies and fight against us and escape from the land." 
>  Therefore they set taskmasters over them to afflict them
>  with heavy burdens. They built for Pharaoh store cities, Pithom and
>  Raamses.
> 
> 
> 

However, we are led by Genesis 15:13 to believe that this was ultimately God's plan.

Does Genesis indicate that this was a punishment for some particular naughtiness on Abram's part or of the People or that there was a particular divine objective?