Aside from being sisters who are both mothers to Angie (Marlene is Angie's biological mother, while Marlene is her acting mother), the two women represent two very different ways of life.
Marlene is an ambitious woman who has left Angie to pursue her career. She is cold in her demeanor and has adapted to the cutthroat culture of her profession. She is politically conservative and looks forward to Margaret Thatcher's tenure in office.
Joyce, on the other hand, has sacrificed her professional ambitions for her family. While Marlene values power and money, Joyce devotes herself to her family, a fact that is noted in the fact that Joyce is raising Angie. Joyce is politically liberal and the two sisters argue over their different points of view. Joyce embodies a more traditional role as a mother while Marlene seeks to achieve success in a man's world.