DNA Structure & Replication Final Exam.

DNA Structure & Replication Final Exam. DNA Replication process by which DNA molecule is copied Chargaff's Law the base compostion of DNA varies between species and for each species, the percentages of A and T bases are roughly equal to the percentages of the G and C bases Double helix two twisted strands Antiparallel polynucleotide strands run in opposite directions 5' -- 3' 3' -- 5' Semiconservative Model the two strands of the parental molecule separate and each functions as a template for synthesis of a new complementary strand Origins of Replication short stretches of DNA having a specific sequence of nucleotides. Enzymes attach here to begin replication. Replication Fork a Y shaped region where the parental strands of DNA are being unwound. Half a replication fork. Helicases enzymes that untwist the double helix at the replication forks, separating the two parental strands and make them available as template strands Topoisomerase The untwisting of double helix causes tighter twisting and strain ahead of replication fork Relieve this strain by breaking swiveling, and rejoining DNA strands Leading strand Strand that continuously adds nucleotides to the new complementary strand as the fork progresses Lagging Strand The strand that DNA polymerase works away from the replication fork; Synthesized discontinuosly as a series of segments Okazaki fragments Series of DNA segments formed on the lagging strand