I use Mr. Andersen's videos all the time in my AP Biology class as a precursor to my lectures. This is my write-a-long, or WAL as I call them, for his "Probability in Genetics: Multiplication and Addition Rules" video.
My WAL is broken into the sections shown within the video multiplication rule, applications, addition rule, applications) and students write along as the video plays. However, at the end of the video, I include an extra probability problem for students to figure out. The answer is not given, as it is expected that students attempt the problem and then discuss answers in class the next day.
Please note that there is no key included with this product. It's good for you to watch the video so you know what your students will see, anyway :)