Chapter 3 An Introduction to Gene Function Central

Chapter 3. An Introduction to Gene Function Central dogma Well-established principle DNA RNA Protein RNA-dependent RNA polymerase (RNA replicase) Ex) influenza virus

Transcription and translation Gene m. RNA ATGACCTTGCATAA TAGTGGAACGTATT AUGACCUUGCAUAA Sense strand antisense s. Coding s. anticoding s. Protein

Biochemical characteristics of amino acids 1. Hydrophobic - Ala, Val, Leu, Ile, Pro, Phe, Met, Gly …. . 2. hydrophilic - Ser, Cys, Tyr, Asp, Glu, Asn, Gln …. . Electronegativity ; In a functional group, each atom has different electronegativity, therefore, a dipole moment is formed to make the group polar.

Biochemical characteristics of amino acids - Hydrophobicity of aa is determined by the electronegativity of the R group and its strength is determined by the difference of electronegativity of the nearby two atoms, not by the absolute value of electronegativity of each atom. For example, in Ser there exists a big difference of electronegativity between O and H of the R group, therefore Ser is included in the hydrophilic aa. -The hydrophilic or hydrophobic characteristics are so importhant because they determine the properties of proteins. Ex) membrane integral protein (Hydropathy plot)

1. Primary structure ; Peptide bond 2. Secondary structure a-helix ; - R-group; protrude outward - right-handed ; 3. 6 residues/turn - keratin - b-sheet ; silk - Turn (random coil) 3. Tertiary structure - Globular P. - Fibrous P. ; silk, keratin, collagen - domain ; Compact structural regions of a protein - Motif ; Domains may contain common structural-functional motifs Zinc finger, leucine zipper Heleix-turn-helix Hydrophobic pocket 3. Quaternary structure - interaction of 2 or more polypeptides

1. transcription Initiation ; close promoter complex, open promoter complex Elongation Termination 2. Translation -Ribosome ; comparison between prok. and euk. size, r. RNA -E, P, A sites Crick’s adaptor hypothesis Structure of t. RNA ; clover leaf structure acceptor stem, D-loop, R-loop, antocodon loop Dr. SH Kim determined the 3 -dimensional structure.

Open reading frame 5’-UTR, 3’-UTR. Transcription start site, initiation codon, termination codon - Prok ; SD sequence - Euk ; first AUG, scanning method

Homework ; compare the mechanism of the translation initiation between prok and euk. 1. f. Met vs. Met 2. ribosome size 3. mechanism for recognition of AUG codon

replication Semiconservative Conservative Dispersive ; experiment of Miselson and Stahl using N 14 and N 15 isotopes Mutation in gene Sickle cell anemia ; 낫모양 적혈구 빈혈증 Mapping by 2 -dimensional peptide electrophoresis ; hemoglobin A and S The 6 th aa Glu (CTC) of the beta chain is mutated to Val (CAC). Hemoglobins form fiber like structure.

Hemoglobin in Sickle cell anemia Normal m. RNA -----CTC---------GAG----- Protein -----Glu----- Sickle Cell m. RNA -----CAC---------GTG----- Protein -----Val-----