AP Biology DNA Structure & Replication | Winston-Salem Forsyth County Schools

University:
Winston-Salem Forsyth County Schools
Course:
AP Biology
Academic year:

2023
Views:

328

Pages:

1
Author:

Vivian Bernard

DNA Structure & Replication ● DNA, & sometimes RNA, is the primary source of heritable information ○ DNA & RNA are composed of nucleotides ● Plasmids: Circular, double stranded DNA molecules that provide genes; may aid in survival of the prokaryotic cell; DNA is synthesized in the 5’ to 3’ direction ● DNA has a negative charge (DNA moves towards the positive/oppositely charged pole) ● Replication is a semi conservative process (the old strand serves as the template for the new strand ● Helicase unwinds the DNA strand by breaking the hydrogen bonds between the nitrogenous base pairs. These strands serve as the template ● Topoisomerase relaxes supercoiling in front of the replication fork ● DNA polymerase 3 requires RNA primers to initiate DNA synthesis ○ Primase facilitates the constructions of RNA primers ○ DNA polymerase synthesizes new strands of DNA continuously (towards the replication fork) on the leading strand & discontinuously (away from the replication fork) on the lagging strand ● DNA polymerase 1 removes the RNA primers & replaces them with nucleotides ● DNA Ligase glues the fragments (Okazaki fragments) on the lagging strand ● DNA Polymerase proofreads newly made DNA & replaces any incorrect nucleotides ● Summarized Process of DNA Replication 1. Helicase unwinds the parental double helix 2. Molecules of SSBP (single stranded binding protein) stabilize the unwounded template strands 3. The leading strand is synthesized continuously in the 5’ to 3’ direction by DNA polymerase 3 4. Primase begins synthesis of the RNA primer for the 5th Okazaki fragment 5. DNA polymerase 3 is completing synthesis 6. DNA polymerase 1 removes the primers & replaces them with nucleotides 7. DNA ligase joins the 3’ end of fragment 2 to the 5’ end of fragment 1