Cameron Diaz has never been a mom, but in her new movie "My Sister's Keeper" she faces a choice no mother would want, which is one reason the actress known mostly for comedic skill stepped into the serious drama.

In the movie opening in U.S. theaters on Friday, Diaz portrays a mom whose daughter suffers from leukemia. So, she gives birth to a genetically engineered second daughter in order to take life-saving umbilical cord blood from the younger sibling and give it to the sick one.

But family relationships are upended when, as girls, the little sister sues her parents to block them from making her give a kidney to her dying sister. Diaz's character, a former lawyer named Sara, fights her 11-year-old daughter's attempt at "medical emancipation" in the serious family drama.

The role is far from Diaz's parts in feel-good movies such as romantic comedy "There's Something About Mary," action-packed "Charlie's Angeles" or voicing the role of Princess Fiona in the "Shrek" animated movies.

Yet Diaz, 36, told Reuters she doesn't see herself as one kind of actress or another -- comedic or dramatic -- and she looks to her own youth in working class neighborhoods of Long Beach, California, for lessons in how real life can get messy.

"I don't feel I've ever played the same person twice. Even though I might have done a couple of comedies or a couple of romantic comedies, the characters are all very different to me," she said.

Nick Cassavetes, son of the late groundbreaking independent filmmaker John Cassavetes, directed "My Sister's Keeper" and said he always saw Diaz for more than her bubbly on-screen personality in fluffy Hollywood tales.

"This is a really wonderful actress and over the next few years you're going to see, she's going to be borne out to be one of the finest actors of our generation," he said.

STRONG SUPPORTING CAST

Oscar-nominated Abigail Breslin, 13, plays younger sister Anna, who is forced to serve as a donor to the older Kate, played by Sofia Vassilieva, 16, who stars in TV's "Medium."

A hotshot attorney (Alec Baldwin) takes Anna's legal case, and faces off against Sara in court. As Kate's health spirals downward, tensions in her family become increasingly strained.

Cassavetes, director of 2004 romantic drama "The Notebook," has a personal connection to the story since his own daughter has lived with a congenital heart defect since birth.

"To work with somebody who was so familiar, so intimate with this situation, this story, made it really easy to trust him," Diaz said about the director.

Diaz said that while it may seem to some of her fans that she leads a soft life in Hollywood, growing up in Long Beach gave her "street smarts."

"The place that I came from it was very urban. There was a lot of lessons to be learned," she said. "I didn't grow up in a protective, sheltered life by any means."

But she feels lucky to have been raised in a working class community by strong parents -- her father died unexpectedly while she was making this movie -- because she learned "a lot of things that are very valuable in my life now."

That experience appears to be paying off in "My Sister's Keeper" because critics are now weighing in and most are giving Diaz and the movie the thumbs up.

"Still better known for her comedic roles ... Cameron Diaz turns in an intense, utterly compelling performance, immersing herself completely (wearing ordinary clothes and sans make-up) in the tough, dramatic role of the matriarch," critic Emanuel Levy wrote on his website.

Source: Reuters