LIFESCI 7A Lecture Notes - Lecture 10: Inosine, Trypsin, Karyotype
Document Summary
Week 7 notes: genomes and regulation in eukaryotes. Bacterial cells package their dna as a nucleoid composed of many loops. Bacterial genomes are circular and dna double helix is underwound (it makes less turns going around the circle than every base can pair with its partner base) Caused by topoisomerase ii, which breaks double helix, rotates to unwind it, then seals it. Nucleoid--formed from supercoils with multiple loops that are bound together by proteins. Proteins + negative supercoiling compress dna into compact volume. Eukaryotic cells package dna as one molecule per chromosome. Packaged with proteins to form dna-protdein complex called chromatin. Dna is wrapped twice around group of histone proteins called a nucleosome. Histone proteins" positive charges are attracted to negative charges of phosphates on dna. Sometimes referred to as 10-nm ber (its diameter) or. Chromosome condensation: chromosomes condense more in preparation for cell division.