what is my legal right in deed of gift?

We reside in Kolkata. We are two children of our parent. Me and my sister. My father passed away in 1979. My mother is still alive. I left the home with my family in 1993 and started residing in my own flat. In 1998, my mother did a registered “deed of gift” of our property (house with few kattahs of land) to my sister. They did not inform me about this deed of gift. Now I came to know that the “deed of gift” was unconditional and was done with sole intention of my mother. I asked my mother why have you done that. She said that her daughter always took care of her and she did it out of blessing to her. If she says like that I have nothing to do as I also feel I’ve never took care of my mother since the time I left home. I also came to know that my sister is selling the house and she has the "parcha" of the property in her name. Actually it was a WB Govt. provided land. After my father died in 1979, my mother became the property owner. WB Govt. has supplied the final ownership deed in the name of my mother in 1988. How can I get back my portion of property being a legal heir? What is my legal right in this case? Can I do a case and win to get back my property? Please advice me what positive legal step can I take?