BI346 Lecture Notes - Lecture 5: Handedness, Writhe, Dna Supercoil
Document Summary
Counter clockwise into wood = left handed helix. Clicker: which one is better example of normal b-dna. A: remember b-dna needs to be right handed and to visualize the right handed from the model. The twist determines the right binding for certain enzymes. Example: a-dna is more compacted, it looks like bdna under pressure and z dna is left: which enzymes bind, how they separate. By coiling the dna instead of linear, it affects the packing of the dna in the cell. It makes it shorter and therefore easier for the cell to contain all the dna. The handedness of the twist determines the way that the super coiling can occur. When two helices pace over each other is a writhe. Need ends of dna fixed = closed dna (the string is tied in a circle) First twist is dna and its twists on itself. This new twist has its own right handed vs. left handed helix.
