BIOL107 Lecture Notes - Lecture 10: Nucleic Acids Research, Tangled, Cell Nucleus

• School: University of Alberta
• Department: Biology (Biological Sciences)
• Course: BIOL107
• Professor: Warren Gallin

Document Summary

Consider the human genome, 6x109 base pairs of dna. Each base pair adds 0. 34x10-9 meters of length. So total length of dna in each cell is ~2 meters, folded into a nucleus with a diameter of ~5x10-6 meters. Every cell cycle the dna is duplicated, and then the chromosomes are condensed without tangling and separated during mitosis. What are cellular mechanisms to avoid having the dna tangled, knotted, unable to separate: hierarchical folding/packaging, topoisomerase enzymes. Topoisomerase ii minimizes dna entanglements by proofreading dna topology after dna strand passage. 3x109 bp of dna per haploid genome, and most cells are diploid so twice that much. Strand length is 0. 34nm/bp, so total length of dna in human cell nucleus is ~2 m long. Diameter of the nucleus is ~ 5 m. Answer: hierarchical folding: dna is complexed with proteins that enable the resulting chromatin to be folded into successively more compact structures.