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Chp . 5 Sec. 1 Notes. DNA. Deoxyribonucleic acid Chromosomes are made of protein & DNA. Genetic material that determines inherited traits. DNA. Made of nucleotides Sugar, phosphate, and a base Identical EXCEPT base 4 bases:. Erwin Chargaff. Chargaff’s Rule:
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DNA • Deoxyribonucleic acid • Chromosomes are made of protein & DNA. • Genetic material that determines inherited traits.
DNA • Made of nucleotides • Sugar, phosphate, and a base • Identical EXCEPT base • 4 bases:
Erwin Chargaff • Chargaff’s Rule: • Amount of adenine (A) equals amount of thymine (T) • Amount of guanine (G) equals amount of cytosine (C).
Rosalind Franklin • British chemist used X-ray diffraction to make images of DNA that helped reveal the structure of DNA. • X-rays are aimed at the DNA molecule and rays that bounce off the molecules are captured on film—Franklin suggests spiral shape.
James Watson & Francis Crick • Concluded that DNA must look like a long twisted ladder. • Built a model. • Helped to explain how DNA is copied & functions in a cell.
Double Structure • Double helix • Two sides of ladder sugar & phosphate • Rungs of ladder pair of bases (A, T, G, C)
Copying DNA • Bases are complementary • A-T • G-C • CGAC GCTG • During replication, molecules split down the middle, where the bases meet.
Copying DNA • DNA is copied every time a cell divides • Job of unwinding, copying, and re-winding the DNA is done by proteins within the cell.