academic dismissive undergraduate and research experience
The only proper answer will come from the admissions system of a university that you apply to. However, in any system that lets you make a personal statement or (better) includes an interview, you will have a chance to explain the issue. Most people, though not everyone, will understand that people change and grow. They also, normally, understand that the more recent work is a better indication of your future work. 

I wouldn't worry too much about it, as long as you have a satisfactory explanation and have made up any learning deficit you may have from the year of poor work.