Authors: Francis Crick
T
HE 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.
1 st position (5’ end) ↓ | 2 nd position | 3 rd 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 |
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 |
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)
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 DNA 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; r
II
; 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
Histones
Hoagland, Mahlon
Hodgkin, Alan
Holley, Robert
Homopolar bonds
Hopkins, Gowland
Hotchkiss, Rollin