.1850 --2005
The
discovery of DNA, RNA and a molecular basis for inheritance involves the history of genetics
.
1850 --2005
British geneticist Charles Waddington wrote that, "It is the order of nucleotides along the double spiral which we have to think of as determining the character of the hereditary material at that region [of the chromosome]." (1962)
In October of 1977, Sir Peter Medawar, a famous biologist wrote that "the greatest scientific discovery of the twentieth century" is "without qualification," the explanation of "the chemical makeup of the compound deoxyribonucleic acid (DNA)."
James D. Watson, a co discoverer of the nucleic acid code, had himself written, in 1980, that the "double helix . . . would revolutionize biology."
Rosalind Franklin, Maurice Wilkins, Francis Crick and James Watson competed with Linus Pauling in a race to discover how proteins were built and what then was the structure of the nucleic acids that code for the parts of proteins which are called amino acids.
Preconditions for development of progress in genetics were four formative stages in the transformation of knowledge:
experimental, discovery, developmental, application
Early
years rediscovery of Mendel's forgotten laws of inheritance
| Cellular biology, fruit flies, corn & chromosomes
| Eugenics
Nucleic acid research | Chemistry,
X-ray crystallography, molecules | Complexity of the
genome | DNA - RNA double helix | Dates
Dates
1859, Darwin's On the Origin of Species published without his awareness of Mendel
1866, Gregor J. Mendel, published "laws of heredity," in peas
1868, Darwin's Variation of Animals & Plants under Domestication
1869, Mendeleyev proposed the periodic law & table of elements
1869, Sir Francis Galton published Hereditary Genius
1882, Koch isolates the bacteria that causes tubercle bacillus, Tuberculosis1900, Hugo deVries, rediscovers the importance of Mendel's work
1901, Amino acid tryptophan was discovered by Sir F. Hopkins
1909 , Wilhelm Johannsen, coins "gene; genotype & phenotype"
1929, Kathleen Lonsdale uses x-rays to examine benzene molecules1930, Arne Tiselius developed electrophoresis for protein research
1934, Dorothy Hodgkin took the first x-ray diffraction photograph
1935, first commercial electron microscope built in England
1944, Erwin Schrødinger published What is Life?
experimental, discovery, developmental, application
Seminal discoveries of the 19th century
techniques, discovered ideas, heuristics, early research
Zeitgeist is the "spirit of the times" and was characterized by a belief in the evolution of life.
Darwin and "a democracy of descent"
Technology altered reality: revealed that there was unseen complexity at the microscopic level:
Microscopy advances, 1742-1840.
Electricity, 1820-1823-1845.
Spectroscopy, 1859-60, cesium & solar spectrum.
X-ray radiation, November 8, 1895 (Wilhelm Konrad Roentgen)
Darwin and breeding by artificial selection,
Mendel and breeding variations in domesticated pea plants
Muller and agronomic chemistry
Morgan and fruit flies
Periodic Table of the elements
radiation as unseen exposure
x-rays -- are very high energy electromagnetic radiation
ultra-violet rays -- are high energy electromagnetic radiation
Classic period: Early years
Rediscovery of Mendel's suppressed work
Mendel's forgotten laws of inheritance
string of beads was the homiletic images Mendel figured were inheritable
breaks or knots
codon–a section of nucleic acid that makes a protein unknown to Mendel.
measures locus; that is where & what shifts
Over time traits survive from one generation to the next that assist organisms in acquiring and digesting food, shelter, nesting sites, security & reproductive success; ... after artificial selection of breeders, Darwin and Wallace called this natural selection.
20th century:
Bateson's work
J.B.S. Haldane's contributions
Theodosius Dobzhansky
Max Perutz, Sir Francis Bragg, & Linus Pauling
chemistry & physiology combine to yield basic information
chromosomes -- dark staining bodies in the nucleus -- fruit flies
physiology & cellular biology was not well understood
Morgan's work with fruit flies, corn and
Barbara McKlintock's work with "jumping genes" were a focus of research due to their relative ease of study.
Eugenics
Social Darwinism, ethnocentrism, & public healthBelief in the perfectibility of human inheritance by eliminating mutant genes and those who possess genetic defects.
legal sterilization of mentally ill (allegedly mental defectives)
identification of allegedly inferior traits, persons and races
Findings--
Genes are located along Chromosomes
gene - set of base pair sequences of DNA that serve to instruct, possessing a particular locus on a long chromosome within the nucleus of eukaryotic cells:
existing between the cellular-nucleo and molecular levels of material existence.
cellular:
organelles & nucleus; within the nucleus is (are)
chromosomal (stained body) information in code.
chromosome is a paired bundle of inheritable traits
molecular: nucleotide = sugar, Phosphate & Nitrogen base
experimental, discovery, developmental, application
Modern period: Nucleic acid research
Chemistry, phage study (viruses), purines & pyrimidines are found in cell nuclei–later purines and pyrimidines are are molecules made of nitrogen base pairs.Double helix -- DNA is comprised of a set of nitrogen bases (4); a sequence of three nitrogen base pairs are what code for an amino acid; held together by five carbon sugar and a phosphate group of molecules.
Discovery stage:
X-ray crystallography, was the means to discover the molecular structure of DNA
1948, Dorothy Hodgkin takes x-ray photos of Vitamin B-12 to determine its molecular structure
1952, Rosalind Franklin, produces an x-ray photograph of DNA that proves it has a double helical structure
1953, Watson & Crick using Franklin's & Wilkin's work est. the nitrogen base sequence or code of nucleic acids
1954, J.B.S. Haldane's book The Biochemistry of Genetics
1990s Lewontin, Not In Our Genes, The Triple Helix
There are three related fields based on levels of complexity necessary to understand genetics.
1: X or Y chromosome:
Chromosomal regions where
loci of traits or diseases are found
sequences of DNA, nitrogen bases
A = T : adenine and thymine, base pairs
G = C : guanine and cytosine, base pairs
3: Molecular:protons bond to form specific atoms (C, O, N, P, S, K)
atoms bond to form molecules (depends on valences)
molecules can bond to form long chains {peptides}
long chained DNA molecules code for amino acids
series of specific amino acids code for proteins and these proteins are essential to all life!experimental, discovery, developmental, application
25 April 1953, Nature; Watson & Crick publish their model of DNA
1955, structure of the protein insulin is described; Severo Ochoa discovers that cellular energy is stored in phosphate bonds & that an enzyme produces RNA in the laboratory!Adenine and nitrogen base bonds with phosphate to carry energy and store energy on the microscopic, cellular or molecular level.
Over time traits survive that assist organisms in acquiring food, shelter, security & reproductive success... Darwin and Wallace called this natural selection. DNA & RNA are the genetic code found in 26 chromosomes (all the strands comprise the human genome, 6 billion pages of instructions for creating a living human.)
The Double Helix, James D. Watson (Mentor, 1968), p. 143.
Findings
Relating time & the cosmos to life’s and human diversity
DNA & RNA are the genetic code for traits found in 26 chromosomes (all the strands comprise the human genome, 6 billion pages of instructions for engendering a living human. 1/3 of the genome codes for parts of the central nervous system.
experimental, discovery, developmental, application
Chromosomes are long coiled strands of nucleic acids because they are found in the cell's nucleus; a walled in security sphere or bubble where inherited information on building proteins are stored.
Upper left are chromosomes' images which are shown on lower right to be coiled around histones (a type of protein).
Nucleic acids are earliest identified in the nuclei of cells where chromosomes –dark staining bodies– from fruit fly studies were found.
Nucleic Acids are both DNA & RNA double helices
Double helix is the shape of the DNA or RNA polypeptide molecule {a really long strand!}
DNA is variable due to the sequential ordering of four nitrogen bases, A, T, C, G. (T becomes U in RNA)
Adenine, Guanine, Cytosine, & Thymine are bases in DNAAdenine, Guanine, Cytosine, & Uracil are bases in RNA
The "sleuths in the search"
The Double Helix, James D. Watson, (New York: Mentor, 1968), 29 Chapters, p. 143.
“how the structure of DNA was discovered” (ix)experimental, discovery, developmental, application
Post-Modern
Application of the findings
The Human Genome Project
"The genome is is the entire set of genetic instructions in the nucleus of every cell. (In fact, each cell contains two genomes, one derived from each parent: the two copies of each chromosome we inherit furnish us with two copies of each gene, and therefore two copies of the genome.) Genome sizes vary from species to species. From measurements of the amount of DNA in a single cell, we have been able to estimate that the human genome --half the DNA contents of a single nucleus-- contains some 3.1 billion base pairs: 3,100,000,000 As, Ts, Cs and Gs."
"in each, it is the DNA that oversees the extraordinary transformation from a relatively simple single cell to the stunningly complex adult of the species,comprised, in the human instance, of 100 trillion cells."
James D. Watson, DNA: The Secret of Life, pp. 165-66.
1988 cooperative venture of the National Institutes of Health and the Department of Energy to:
codify, describe, diagrammatically detail and examine the 4 billion genes of the 46 human chromosomes.
The human genome.
experimental, discovery, developmental, application
Feedback concept
Meade’s original definition in 1924: (Search for Solutions).
Han’s Selye’s descriptive (linguistic) description of the stress response syndrome
translation from verbal (linguistic) to visual (graphical).
Freeman Dyson’s “global application” (Infinite in all Directions).
Garrett Hardin’s relation of feedback to ecology & human biology
(thermostat as templates a double translation of visual and verbal to graphical to model).
Gregory Bateson’s “model” of ecological & human physical relations
(verbal translation to graphical representation that is both analytical & synthetic).experimental, discovery, developmental, application
Basic ingredients
Phenotype -- the expression or external appearance of inherited traits: complexion, eye color, dentition, hair color, blood type, immune response, etc.
Genotype -- the underlying base pair sequences that together form the gene that codes for proteins, structures, hormones, enzymes, or neurotransmitters in the body of all living things.
In Eukaryotic organisms this genetic material is usually in the nuclei of cells, but the maternal line of inherited material can be traced in the mitochondrial DNA.
Nitrogen base pairs make up the RNA and DNA polypeptide chains (long molecules).
DNA & RNA
"Every protein is synthesized according to instructions contained in DNA."
(Starr, p. 162)
In retroviruses the instructional transfer is reversed from RNA to DNA.
Types of molecules involved in replication:
DNA RNA messenger, ribosomal, transfer A Adenine C Cytosine G Guanine Thymine Uracil
"It takes three pairs to specify an amino acid."
Amino acids in long strings fold to make complex proteins that regulate bodily performance, function and development by making catalytic enzymes, markers or pheromones, and signals or hormones that direct responses of organs and organ systems throughout the body.
experimental, discovery, developmental, application
"junk" DNA
"Junk DNA got its name because the nucleotides there do not encode instructions for making proteins, the basis of life."
"…the vast material in organisms from bacteria to mammals consists of non coding DNA segments, which is interspersed with coding parts. In humans, about 97 percent of the genome is junk."
"junk DNA contains three to four times the redundancies of the coding segments."
("Talking Trash," Philip Yam, Sci. Amer.; 3/95, p. 24)
Responses of genes to environmental disturbances:
radiation & mutation
Nitrogen base pairs undergo numerous transcription
"it takes three pairs to specify an amino acid"
--------> -------------> ----> produces an
DNA transcript amino acid
codon RNA
Adenine -- Uracil A == U
Guanine -- Cytosine G == C > serine
Cytosine -- Guanine C == Ggenetic counseling
congenital sicknesses
disease [inheritable] gene loci Huntingtons Chorea chromosome 4 Cystic fibrosis chromosome 7 Alzheimer's chromosome 19 Amytrophic L. sclerosis chromosome 21 Colon cancer chromosome 2
experimental, discovery, developmental, application
genetic engineering
Hormonal regulation controls growth and reproduction of creatures
progesterone -- genes that code for this protein ultimately influence the menstrual cycle and that cycle directly influences the reproductive potential.
estrogen -- receptors for this protein are found in both sexes but influence many female traits.
epinephrine -- is involved in fight or flight responses of creatures to stress, fear, and adaptation.
GMOs or Genetically Modified Organisms
Dr. Charles Sing, University of Michigan.
"What is a good gene and what is a bad gene depends on how you treat it." [genotype]
"Genes don't wake up [phenotype] until they are exposed to some environmental factor."
Dr. Richard Strohman, UC Berkeley
"the presence of a genetic marker . . . is no guarantee that abnormality or disease will show up."
[ 12/6/93, p.55, Newsweek ]
genetophobia
Frankenstein monster or Faustian bargain?
Critic, Jeremy Rifkin
Defender, James Watson
experimental, discovery, developmental, application
Vocabulary
The vocabulary of modern inheritance is confusing and because it is so specialized includes three or more levels of material organization beyond our comprehension because we can not see to such depths of the organic structure we call nature.
new words old words genome Mendelian inheritance nucleic acids genetic material characteristics genes genetic traits chromosomes dark stained cellular bodies nucleotides heredity (in cells' nucleus) DNA or RNA alleles (pairs of material) nitrogen bases purines & pyrimidines P,O, H2O, N, C elements found in nucleic acids retrovirus virus Genosystem gene experimental, discovery, developmental, application
Dozen layers of complexity in science of life and the cosmos
Up to the top of the stairway of order, because they can be very big
Bottom of the stairway of order, because they are very, very small.
What is at the bottom?
subatomic quarks, leptons, bosons
atomic neutrons, protons, electronsAtoms
elements: C H O P K I N S' Ca Fe or ( C. Hopkin's Cafe )
molecular:
H2O (water) compound
bases adenine = thymine; guanine = cytosine
helix shape of DNA & RNA molecule
three bases code for an amino acid (21)
sequence of N bases = sequence of the amino acids
sequence of amino acids = protein, hormone, enzyme
sequences of DNA or RNA = traits on chromosomesThree base sequences code for amino acid, the building blocks of proteins.
Proteins, catalysts, hormones; the micro machinery of life.
Organelles, like mitochondria have their own DNA
Cells normally have DNA in the organelles and packed into the nucleus .if these are Eukaryotic cells.
Up to the top of the stairway of order, because they can be very big cells
experimental, discovery, developmental, application
Modern science’s worldview of evolutionary continuity as the descent from a common species.
There is an ongoing unfolding of organization as the universe ages
Cosmos evolves ----> galaxies evolve
stars evolve and supernova ------------> creating all 109 elements
nickel & iron are earth’s core
earth evolves -- plate tectonics ------------> creating Continents & Oceans
habitats evolve due to sedimentation & erosion
biological creatures adjust to changing habitats
life by means of natural selection changes into varied forms.
Index
About genes and genomesApplied genetics
Chromosome
Critics
dates & eventsdetails of the human genome
Development stage
developmental preconditions
Discovery stage
DNA & RNA relationsEugenics movement
Experimental stage
Formative period
FoundationsHistory of Genetics
Key developments
subject index
Vocabulary
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