Chromosome structure & Organelle DNA

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Chromosomes are structures that look like thread, which live in the nucleus (center) of cells. One molecule of DNA and one protein make up one chromosome. Chromosomes are different sizes, and proteins... called histones allow them to pack up small enough to fit in a nucleus Chapter 11: Chromosome Structure and Organelle DNA11.1 Large Amounts of DNA Are Packed into a Cell- packaging of tremendous amounts of genetic information into small space = ultimate storage problem- 3 hierarchal levels:- primary: nucleotide sequence- secondary: 3-D sequence (helix)- tertiary: folding and packing into chromosome supercoiling: tertiary structure where DNA Helix is subjected to strain due to underwound or overwound- relaxed state: B-DNA (10bp per 360 rotation) - if energy is used to add or remove turns, strain is placed on molecule -> supercoil (twist on itself)- positive supercoiling: over-rotated (adding one bp per 360 rotation)- negative supercoiling: under-rotated (think of removing one bp per 360 rotation)- partial solution to packing problem since it occupies less space than relaxed DNA- takes place when strain cannot be compensated by turning the ends of double helix (as the case in circular DNA) [Show More]

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