It is in Act Two that Mama assumes her role of matriarchal dominance by choosing on behalf of her family how to spend the money she has received. She has chosen to put a down payment on a house. It is interesting to note the different reactions to this news. Ruth is overjoyed, especially because of the baby she is now carrying. Mama too is looking forward to having a yard so that she can grow some flowers, but Walter is depressed because Mama would not let him have the money for his liquor business.
However, in the next scene, Mama has an apparent change of heart, entrusting the rest of the money that she gained to Walter to put some aside for Beneatha's schooling and then to invest the rest as he sees fit. She explains her reasoning, for this change of heart by saying:
I say I been wrong son. That I been doing to you what the rest of the world been doing to you... There ain't nothing as precious to me... There ain't nothing worth holding on to, money, dreams, nothing else - if it means - if it means it's going to destroy my boy... It ain't much, but it's all I got in the world and I'm putting it in your hands. I'm telling you to be the head of this family from now on like you supposed to be.
Mama therefore relinquishes her position of matriarchal dominance over the family that she had assumed when her husband died, allowing her son to take the patriarchal role of head of the family.