Biology 1002B Lecture Notes - Lecture 4: Deoxyribose, Polynucleotide, Cytokinesis
Document Summary
Two of the bases (adenine and guanine) are purines and the other two (thymine and cytosine) are pyrimidines. Purines bond with pyrimidines (a and t, c and g). These relationships are chargaff"s rules. In rna, thymine is replaced with uracil. The base pairing remains the same (a with u) This is complementary base pairing. The dna incorporates the denser nitrogen into its structure. The deoxyribose sugars are linked by the breaking of phosphate groups. This means dna polymerase can only add molecules at the 3i end (on the hydroxyl group) The other must be replicated in short strands called okazaki fragments away from the replication fork. Leading strand: the new strand of dna synthesized in the direction of unwinding. Lagging strand: the new strand of dna synthesized in the direction opposite unwinding: general action of proteins in fig. 12. 15: dna helicase unwinds the dna. Double helical structure of dna, two antiparallel backbones (run in opposite directions)