DNA Structure and Replication Quiz

DNA = Deoxyribonucleic Acid - Nucleotide

Comprised of ==3 parts - 5-carbon sugar (deoxyribose), phosphate, nitrogenous base==
2 Types Nitrogenous Bases: Purines (2 rings) and Pyrimidines (1 ring) * Purines: Adenine, Guanine * Pyrimidines: Cytosine, Thymine * Adenine pairs with Thymine (A&T) * Guanine pairs with Cytosine (G&C) * ==Bases held together by hydrogen bonds==
Percentage of Bases in DNA * percentage of A (Adenine) = percentage of T (Thymine) * Shape of DNA - Double Helix * 2 antiparallel strands - phosphate-sugar backbone * ==Phosphate and sugar held by covalent bonds== * percentage of C (Cytosine) = percentage of G (Guanine)

\ 1. Nucleotide chains separated at the replication fork by enzyme ==Helicase== - breaks hydrogen bonds between bases
\ 2. ==SSBP (Single-Strand Binding Proteins)== attach to the separate strands, prevent them from coming back together
\ 3. ==Primase== makes RNA primer to signal starting point to DNA Polymerase
\ 4. ==DNA Polymerase III== binds to primer, adding nucleotides to the 3’ of the separated strands * Synthesis is always bidirectional - ==always made in the 5’-3’ direction==
Leading Strand * Continuous strand that is made in the direction of the replication fork
Lagging Strand * Discontinuous strand made in the opposite direction of the replication fork * ==Okazaki Fragments==: sections of DNA about 100-200 base pairs long on the lagging strand * ==Ligase== ‘glues’ all the okazaki fragments together * ==Topoisomerase== cuts and rejoins the DNA downstream of the replication fork
Semi-Conservative Replication * When replication is finished, you get the ==original strand and a newly made daughter strand==