Chapter 3 DNA RNA and Protein Synthesis Processing

Chapter 3. DNA, RNA, and Protein Synthesis

Processing of Genetic Information DNA Replication Transcription m. RNA Translation Protein r. RNA t. RNA

Overview of Basic Molecular Genetic Process

Primary Structure : Nucleotides Base Nucleoside Nucleotide Adenine Adenosine Adenylate Guanine Guanosine Guanylate Cytosine Cytidylate Thymine (D) Thymidine Thymidylate Uracil (R) Uridine Uridylate Purine Pyrimidine H 2’-Deoxyribose RNA DNA

Nucleoside AMP : Adenosine monophosphate d. CDP : Deoxycytidine diphosphate d. GTP : Deoxyguanosine triphosphate

Bases

Nucleic Acid Strand

DNA Double Helix n DNA double helix structure ¨ Two antiparallel chains of deoxyribose-phosphate backbone ¨ Two chains are joined by complementary base pairing n n n A: : T, G: : : C Hydrogen bonding DNA size ¨ Indicated by the number of base pairs ¨ Kb: 103 bp, Mb: 106 bp

DNA Structure Minor groove Major groove

0. 26 nm 0. 34 nm Models of Various Known DNA Structures In very low humidity RNA-DNA, RNA-RNA helix Short DNA with alternating purine and pyrimidine (Gs and Cs)

Base Paring H Uracil (U) Purine Pyrimidine

DNA Replication • Semiconservative DNA synthesis • 5’ to 3’ polymerization by DNA polymerase • Nucleoside triphosphates (NTPs) as substrates

Formation of polynucleotide chains

DNA Replication n Replication Origin ¨ ¨ n Bidirectional Replication ¨ ¨ n 100 to 200 bp sequence region Recognized by origin recognition proteins Prokaryotes: one replication origin Eukaryotes: multiple replication origins (thousands. . ) Two replication forks Replication bubbles Speed of Replication ¨ ¨ E. coli: 1000 bp/sec, 5 Mbp Human: 50 bp/sec, 3000 Mbp

DNA replication (1) n n n Helicase ¨ Unwind DNA Single strand DNA binding protein Primase ¨ n Synthesis of RNA primer DNA polymerase ¨ Synthesis of DNA n Leading and lagging strand ¨ E. coli DNA Pol III

DNA replication (2) DNA Pol I: Remove RNA primer by 5’ to 3’ exonuclease activity and replace the RNA with DNA Ligase: Join Okazaki Fragments

Homework Draw DNA structure of d. Gd. Td. Cd. A