What Mad Pursuit

by Francis Crick

  APPENDIX B

  The Genetic Code

  THE GENETIC CODE is the little dictionary that relates the four-letter language of the nucleic acids (A, G, T, and C for DNA; RNA has U in place of T) to the twenty-letter language of proteins. A group of three adjacent letters, called a codon, codes for an amino acid. (There are 4 × 4 × 4 = 64 codons in all.) Most amino acids are coded by more than one codon. In addition, three codons stand for “end of chain.”

  The genetic code is usually displayed as shown in table B-1. At first sight the table may appear rather confusing, but basically it is very simple. The exact chemical formula of each amino acid is known. For example, one of the amino acids is called valine. To make the table easier to read, valine is abbreviated to Val. In a similar way histidine, the name of one of the other amino acids, is written His. The three bases of each triplet can be read off for each entry in the table. The first base is written on the left, the second at the top, and the third on the right. Thus it can be seen that valine (Val) is coded by GUU, GUC, GUA, and GUG, whereas histidine (His) has the codons CAU and CAC. The three codons for ending the polypeptide chain (STOP) are UAA, UAG, and UGA. The left end of an RNA or DNA chain, as usually written, is called the 5’ end and the right end the 3’ end, for chemical reasons.

  1st position

  (5’ end)

  ↓ 2nd position 3rd position

  (3’ end)

  ↓

  U C A G

  U Phe

  Phe

  Leu

  Leu Ser

  Ser

  Ser

  Ser Tyr

  Tyr

  STOP

  STOP Cys

  Cys

  STOP

  Trp U

  C

  A

  G

  C Leu

  Leu

  Leu

  Leu Pro

  Pro

  Pro

  Pro His

  His

  Gin

  Gin Arg

  Arg

  Arg

  Arg U

  C

  A

  G

  A lie

  lie

  lie

  Met Thr

  Thr

  Thr

  Thr Asn

  Asn

  Lys

  Lys Ser

  Ser

  Arg

  Arg U

  C

  A

  G

  G Val

  Val

  Val

  Val Ala

  Ala

  Ala

  Ala Asp

  Asp

  Glu

  Glu Gly

  Gly

  Gly

  Gly U

  C

  A

  G

  TABLE B-1

  The code appears to be exactly the same for all higher plants and animals studied so far. Nevertheless, minor variations are known, especially for the DNA of certain mitochondria, the little organelles that live in the cytoplasm of higher organisms and for certain of the fungi.

  Abbreviations

  U

  C

  A

  G Uracil(for DNA, read T [Thymine] instead of U)

  Cylosine

  Adenine

  Guanine

  Ala

  Arg

  Asn

  Asp

  Cys

  Gln

  Glu

  Gly

  His

  Ile

  Leu Alanine

  Arginine

  Asparagine

  Asparlic acid

  Cysteine

  Gluiamine

  Glutamic acid

  Glycine

  Histidine

  Isoleucine

  Leucine Lys

  Met

  Phe

  Pro

  Ser

  Thr

  Trp

  Tyr

  Val

  STOP means "end chain" Lysine

  Methionine

  Phenylalanine

  Proline

  Serine

  Threonine

  Tryptophan

  Tyrosine

  Valine

  Index

  Acridines

  Adaptor hypothesis

  Adenine

  Admiralty

  Adrian, Lord

  Alanine

  Albright, Thomas

  Algorithms

  Ames room

  Amino acids; adaptors and; alteration of single; DNA and RNA templates for side-chains of; head-tail joining of in polypeptide chain; mutants and; one-dimensional sequences of; polypeptide chains and; in proteins; sequences of; side-chains; total number of; tRNA and; see also specific omino acids

  Amylase

  Andersen, Richard

  Andrade, Edward Neville da Costa

  Antibiotics, advances in

  Antibodies, monoclonal

  Arginine

  Arrhenius, Svante

  Artificial intelligence (AI)

  Asimov, Isaac

  Asparagine

  Astbury, William; α helix and

  Astrachan, Lazarus

  Astronomy

  Asymmetric unit

  Atomic energy

  Atoms: Bohr theory; carbon; distance between; energies between; exact configuration of in space; heavy; hydrogen; light; mercury; nitrogen; smashing of by Cockcroft and Walton

  Attention, neural basis of

  Autocorrelation function, of electron density

  Avery, Oswald

  Bachmann, Larry

  Backmutation

  Back-propogation algorithm

  Bacteria; blender experiment and; diaminopimelic acid found in cell walls of; difference between genotype and phenotype and; gene control and; genetics and; introns and; lysis of; rough coat; smooth coat; see also Bacteriophages; Phages

  Bacterial Cell, The (Hinshelwood)

  Bacteriophages; see also Bacteria; Phages

  Baltimore, David

  Barlow, Horace

  Barnett, Leslie

  Base pairs: DNA; mutation rate in effective; pairing rules for; replication errors and; RNA; see also Nucleotides

  Bauer, William

  Beadle, George

  Behavioral genetics

  Behaviorism

  Benzer, Seymour; behavioral genetics of Drosophila and; Biochemical Congress at Moscow (1961) and; one-dimensionality of gene and

  Bernal, J. D.

  Bessel functions

  ß-galactosidase

  Big Bang theory

  Biochemical Congress, Moscow (1961)

  Biochemistry

  Biological replication, natural selection and

  Biology: development of theory in; difference of from physics; entry of physicists into; hydrogen bond and; laws of; mechanisms of

  Biophysics

  Birkbeck College, London

  Black box: brain as; classical genetics as

  Blender experiment

  Blending inheritance

  Blind Watchmaker, The (Dawkins)

  Blue-green algae; see also Bacteria

  Bohr, Niels

  Bondi, Hermann

  Bonds: atomic; distances of; double; electrostatic interactions of; homopolar; hydrogen; multiple; peptide; single; and van der Waal's forces

  Botany

  Boyton, Robert

  Brachet, Jean

  Bragg, Sir Lawrence; α helix and

  Bragg, Sir William

  Bragg's law for X-ray diffraction

  Brain: ablation of; as black box; cerebral cortex; hippocampus; mammalian; memory and; models of; neocortex; as product of natural selection; receptors; reflectivity and; sciences; transmitters; visual system; waves; workings of

  Brenner, Sydney; embryology and; genetic code work by; mRNA work by; neurobiological interests of; paper on triplet code; phage genetics work by

  Bressler

  British Broadcasting Corporation (BBC)
r />   Bromotyrosine

  Bronowski, Bruno

  Brooklyn Polytechnic

  Buchner, Edward

  Caenorhabditus elegans

  Caius College

  California

  California Institute of Technology

  Callander, Jane

  Cambridge University; see also specific colleges

  Carbon

  Carboxyl (CO) groups

  Carnegie-Mellon University

  Cartilage

  Catholic Church

  Cavendish, Henry

  Cavendish Laboratory

  Central dogma

  Cerebral cortex

  Chadwick, James

  Chain terminators

  Chargaff, Erwin

  Chargaff's rules

  Chemical and Engineering News

  Chemistry; of DNA; inorganic; lack of knowledge of on part of many physicists; of macromofecules; Nobel Prize for; organic; of polypeptide synthesis; protein; quantum mechanics application to

  Chick: fibroblasts, phagocytosis of magnetic ore by; lysozyme

  Chromatography; protein fingerprinting and; tRNA and

  Chromosomes: approximate size of; DNA in; occurrence of cell genes on; selfish DNA in

  Churchland, Pat

  Churchland, Paul

  Church of England

  Circular DNA

  Cis-trans test

  Cistrons

  Cochran, William

  Codons

  Cognitive science

  Cohn, Mel

  Coil of Life, The (Moore)

  Cold Spring Harbor: annual meeting (1966); Symposium (1953)

  Co-linearity

  Colinvaux, Raoul

  Collagen

  Collingwood, Edward

  Color vision

  Combination code

  Comma-free code

  Commoner, Barry

  Complexity: biological; species

  Condensation

  Cones, number of in eye

  Congregational Church

  Consciousness: experimental study of; mystery of

  Conservation laws

  Continuous creation theory

  Cosmology

  Coulson, Charles

  Cowan, Max

  Cowan, Pauline

  Cozzarelli, Nick

  Creationism

  Crick, Anne Elizabeth (née Wilkins)

  Crick, Arthur

  Crick, Doreen (née Dodd)

  Crick, Francis: adaptor hypothesis and; α helix and; Biochemical Congress at Moscow (1961) and; biological training of; biophysics and; birth; botanical interests of; brain visual system and; Cambridge home of; chemistry training and; childhood and early years of; collagen work by; directed panspermia and; divorce of; DNA double helix codiscovery by; DNA structure work by; early molecular biology interests of; early pure scientific research of; early scientific interests of; early work experience of; education of; embryology and; error-correcting device in DNA replication and; experiences with books and movies about DNA; extraterrestrial intelligence interests of; family life of; feelings on discovery of double helix; first crystallographic talk of; first marriage of; first published papers of; first research seminar of; genetic code work; "gossip test" theory of, raduate school and; mpressions of The Double Helix, later years of; Life Itself ; mathematics and; mRNA work by; neurobiological interests of; Nobel Prize awarded to; paper on comma-free code; papers on DNA structure; paper on genetic code; paper to Society of Experimental Biology; paper on triplet code; phage genetics work by; Ph.D. thesis of; physics training and; protein fingerprinting research by; protein structure research by; religious views of; RNA Tie Club and; Scientific American article by; scientific intelligence experience of; on scientific research as an activity; second marriage of; "selfish DNA" work by; on sound biological theory; sports interests of; suppressors and; Tangier meeting and; weapons research during World War II; X-ray crystallography work and

  Crick, Harry

  Crick, Jacqueline

  Crick, Michael

  Crick, Odile

  Crick, Tony

  Crick, Walter

  Crosses, gene

  Cross-feeding

  Cross-overs

  C2 space group

  Cysteine

  Cystine

  Cytoplasm; physical properties of; and ribosomal protein synthesis; RNA export to; RNA in

  Cytosine

  Darwin, Charles: blending inheritance and; invalidation of creationism by; Linnean society and; natural selection theory of

  da Vinci, Leonardo

  Dawkins, Richard

  de Hoffmann, Frederic

  Delbrück, Max

  Deletions; overlapping

  Demerec, Milislav

  Deoxyribonucleic acid, see DNA

  Deoxyribose

  Diaminopimelic acid

  Dickerson, Richard

  Dihedral angle

  Dinosaurs, extinction of

  Diploidy

  Diversity, of species

  DNA: A form; α helix; backbone of; bacterial cell; ß helix; B form; books and movies about; chemistry of; chromosomal; circular; coding for proteins; composition of genes, control sequences for gene induction and repression; C2 space group; double helix; ease of understanding concept of; error-correcting device in replication of; fibers; four-letter alphabet of; impurities in; left-handed structure; length of presence on Earth; linking number and; linking of unlinked circles of; mitochondrial; molecule length; molecule shape; molecule size; mutation rate per effective base pair and; nonsense sequences; nuclear; as nucleoprotein constituent; origin of; parasitic; phage; phosphate groups; recombinant; recombinant techniques in Drosophila genetics; radiation and; replication; selfish; sequence complementarity of; sequencing; side-by-side structure theory of; single-stranded; structural similarity to RNA; structure of; sugar groups; as template for amino acid side chains; transforming factor of pneumococcus and; two chains of; unlinking of linked circles of; viral; Z-; see also Base pairs; Nucleotides

  Dominance: allelic; incomplete

  Donohue, Jerry

  Doty, Paul

  Double Helix (movie),

  Double Helix, The (Watson),

  Dreams, theory of

  Dreyer, William

  Drosophila

  Dulbecco, Renato

  Dyadic symmetry

  Earth, true age of

  Eccles, Sir John

  E. coli: bacteriophage T4 infection of; introns and

  Egg, sexual reproduction and

  Egg white lysozyme

  Eigen, Manfred

  Eigenvalues

  Eighth Day of Creation, The (Judson)

  Electron: density; density mapping; discovery of; microscope

  Electrostatic interactions

  Embryology

  Encounter

  End chains; STOP codon and

  Energy: of attraction; free; of repulsion

  Environment, role of in natural selection

  Enzymes; induction of; pancreatic production of

  Ephrussi, Boris

  Error-correcting device

  European Conference on Visual Perception, Seventh, (Cambridge)

  Evolution; α helix and; difficulty in studying; hostility of creationists toward; natural selection and; process of; of stars; over time; as tinkerer

  Experimental Cell Research

  Extinction, of species

  Eyes, photoreceptors of

  Fell, Honor B.

  Fermentation

  Feynman, Richard

  Fibroblasts, chick

  Fibrous proteins

  Fisher, R. A.

  Fivefold symmetry; α helix and

  Fleming, Alexander

  Fodor, Jerry

  Formylmethionine

  Fossil record

  Fouracre, Ronnie

  Fourier Transforms

  Fractionation methods

  Franklin, Rosalind; and A form DNA; and B form DNA; movie characterization of; paper on DN
A structure; personal background of; and Tobacco Mosaic Virus; X-ray crystallography work on DNA structure

  Free energy

  Freese, Ernst

  Freud, Sigmund

  Freudenthal, H.

  Frog's eye, insect detectors in

  Fundamental particles

  Galactose

  Gamow, George

  General Chemistry (Pauling)

  Gene(s): and amino acid sequence in proteins; bacterial transformation and; chemical structure of; control of bacteria; control of protein synthesis; cross-over; crosses; cytoplasmic; deletions; DNA between; DNA composition of; frequency of recombination; hybrid; induction; isolation; eaky mutants; magnification; mapping; molecular structure of; mutants; nature of; nonleaky mutants; nuclear; occurrence of on chromosomes; omissions; polysaccharide coats of; products; protein component of; protein synthesis control by; rII; random mutation; replication; repression; RNA intermediate in protein synthesis and; size of; structure; suppressors; three-dimensional structure of; transfer of bacterial; tRNA; wild-type; as units of instruction; see also Genetic code; Genetics; Mutations

  Genetic code; combination code; comma-free code; elucidation of; triplet code; uniformity of; universality of; see also Gene(s); Genetics; Mutations

  Genetic disease

  Genetics: bacterial; behavioral; classical; control mechanisms; crosses; general ignorance toward; Mendelian; molecular basis of; phage; recombination; of speciation; variation; see also Gene(s); Genetic code; Mutations

  Genotype

  Geophysics

  Glasgow University

  Globular proteins

  Glutamate, NMDA receptor for

  Glutamic acid

  Glutamine

  Glycine

  Gold, Thomas

  Goldblum, Jeff

  "Golden Helix, The,"

  Golomb, Sol

  Gosling, Raymond

  Gradients

  Green College

  Griffith, John

  Group theory

  Guanine

  Haldane, J. B. S.

  Hamlet (Shakespeare)

  Handedness, of biological molecules

  Haploidy

  Hardy Club

  Hartridge, Hamilton

  Harvard Medical School

  Hauptman, Herbert

  Hayes, William

  Helix: α double; integer axes of; molecular simplicity of; noninteger screw of; Pauling's α; peptide bonds planar in; screw axis of

  Helmholtz Club

  Hemoglobin; heavy atoms added to; horse; human; structure of; three-dimensional structure of; X-ray diffraction studies of

  Hershey, Al

  Hill, A. V.

  Hinshelwood, Sir Cyril

  Hippocampus