Site Map
Classical Genetics
Children resemble their parents.
(Gregor Mendel: introduction)
- CONCEPT
- Since the beginning of human history, people have wondered how traits are inherited from one generation to the next.
- ANIMATION
- Gregor Mendel explains how traits are inherited.
- GALLERY
- Early ideas on inheritance
- VIDEO
- Robert Olby
- BIO
- Johann Gregor Mendel — Father of Genetics
- PROBLEM
- Test your knowledge of Mendel's techniques.
- LINKS
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Genes come in pairs.
(Gregor Mendel: genetic alleles)
- CONCEPT
- Mendel deduced that pure-bred parents have two copies of the same gene for each trait.
- ANIMATION
- Gregor Mendel explains how he discovered that genes come in pairs by studying pea plants.
- GALLERY
- Mendel and his peas
- VIDEO
- Robert Olby
- BIO
- Johann Gregor Mendel — the Man, the Monk
- PROBLEM
- Repeat Mendel's experiments with an eighth trait.
- LINKS
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Genes don't blend.
(Gregor Mendel: inheritance)
- CONCEPT
- Mendel discovered that pure-bred plants did not produce offspring with blended traits.
- ANIMATION
- Gregor Mendel explains that breeding short and tall pea plants didn't produce a medium-sized plant.
- GALLERY
- Mendel’s experimental notes and specimens
- VIDEO
- Robert Olby
- BIO
- Johann Gregor Mendel — the Scientist
- PROBLEM
- Breed pea plants to observe flower color.
- LINKS
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Some genes are dominant.
(Gregor Mendel: dominance)
- CONCEPT
- Mendel identifies dominant and recessive genes.
- ANIMATION
- Gregor Mendel explains the rules of inheritance.
- GALLERY
- Commemorating Mendel
- VIDEO
- Robert Olby
- BIO
- Johann Gregor Mendel — the Unappreciated
- PROBLEM
- Cross pure-bred pea plants to identify dominant flower color.
- LINKS
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Genetic inheritance follows rules.
(Punnett squares)
- CONCEPT
- Different gene combinations result in different dominant/recessive ratios in offspring.
- ANIMATION
- Reginald Punnett and William Bateson explain Mendel's ratios.
- GALLERY
- Punnett portrait and Bateson photos and correspondence
- VIDEO
- Robert Olby
- BIO
- Reginald Crundall Punnett, William Bateson
- PROBLEM
- Perform a dihybrid cross.
- LINKS
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Genes are real things.
(rediscovery of Mendel's laws)
- CONCEPT
- The study of the cell and chromosomal behavior confirmed Mendel's work.
- ANIMATION
- Hugo de Vries, Carl Correns, and Erich von Tschermak-Seysenegg explain the laws of heredity, and Theodor Schwann introduces cellular microscope discoveries.
- GALLERY
- de Vries, Correns, and von Tschermak-Seysenegg photos
- VIDEO
- Robert Olby
- BIO
- Hugo de Vries, Carl Erich Correns, Erich von Tschermak , Robert Hooke, Theodor Schwann
- PROBLEM
- Visualize cells.
- LINKS
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All cells arise from pre-existing cells.
(mitosis)
- CONCEPT
- An overview of the discovery of cell division, mitosis.
- ANIMATION
- Walther Flemming explains the phases of mitosis.
- GALLERY
- Photomicrograph of a cell dividing
- VIDEO
- Garland Allen
- BIO
- Walther Flemming
- PROBLEM
- Look at the chromosome number of fruit flies.
- LINKS
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Sex cells have one set of chromosomes; body cells have two.
(meiosis)
- CONCEPT
- Offspring arise from the union of specialized sex cells — a female egg and a male sperm.
- ANIMATION
- Theodor Boveri presents chromosomes' role in development.
- GALLERY
- Boveri portrait, meiosis, and a karyotype
- VIDEO
- Scott F. Gilbert
- BIO
- Theodor Boveri, Walter Stanborough Sutton
- PROBLEM
- Take a look at human chromosomes.
- LINKS
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Specialized chromosomes determine gender.
(sex chromosomes)
- CONCEPT
- Study of meiosis revealed the chromosomal basis of gender.
- ANIMATION
- Nettie Stevens and Edmund Wilson explain how gender is determined by special chromosomes.
- GALLERY
- Stevens and Wilson photos.
- VIDEO
- Garland Allen
- BIO
- Nettie Maria Stevens, Edmund Beecher Wilson
- PROBLEM
- Try your hand at sex determination.
- LINKS
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Chromosomes carry genes.
(fruit fly genetics)
- CONCEPT
- Fruit flies help to reveal that chromosomes carry genes.
- ANIMATION
- Thomas Hunt Morgan describes his discoveries using fruit flies.
- GALLERY
- Morgan , fruit flies, and the fly room
- VIDEO
- Garland Allen
- BIO
- Thomas Hunt Morgan
- PROBLEM
- Perform some fruit fly crosses.
- LINKS
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Genes get shuffled when chromosomes exchange pieces.
(genetic recombination)
- CONCEPT
- Linkage groups on chromosomes gave clues to where genes are located.
- ANIMATION
- Alfred Sturtevant describes gene mapping.
- GALLERY
- Sturtevant and Bridges photos
- VIDEO
- Garland Allen
- BIO
- Alfred Henry Sturtevant, Calvin Blackman Bridges
- PROBLEM
- Determine gene linkage in fruit flies.
- LINKS
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Evolution begins with the inheritance of gene variations.
(early plant genetics, evolution)
- CONCEPT
- Changes in genes over time lead to evolution.
- ANIMATION
- George Shull used corn to study gene variation.
- GALLERY
- Darwin and his home, Shull portrait
- VIDEO
- Garland Allen
- BIO
- Charles Robert Darwin, George Harrison Shull
- PROBLEM
- Explore "hybrid vigor."
- LINKS
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Mendelian laws apply to human beings.
(sex-linked genes, early human genetics)
- CONCEPT
- Family pedigrees provided evidence of Mendelian inheritance in humans.
- ANIMATION
- Queen Victoria explains pedigrees using the royal family and its inheritance of hemophilia.
- GALLERY
- Garrod and correspondence on brachydactyly
- VIDEO
- Garland Allen
- BIO
- Sir Archibald Edward Garrod
- PROBLEM
- Trace alkaptonuria through a family pedigree.
- LINKS
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Mendelian genetics cannot fully explain human health and behavior.
(eugenics)
- CONCEPT
- The eugenics movement applied Mendel's laws to complex human behaviors.
- ANIMATION
- Charles Davenport applies Mendel's laws to thalassophilia.
- GALLERY
- Davenport, eugenics personnel and publications
- VIDEO
- Garland Allen
- BIO
- Charles Benedict Davenport
- PROBLEM
- Examine some family pedigrees to determine inheritance of traits.
- LINKS
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Molecules of Genetics
DNA and proteins are key molecules of the cell nucleus.
(DNA and amino acid discovery and structure)
- CONCEPT
- DNA and protein are candidates for transmitting hereditary information.
- ANIMATION
- Friedrich Miescher and Phoebus Levene research nuclein, protein. and DNA.
- GALLERY
- Miescher, Levene and their laboratories
- VIDEO
- Thomas Sakmar
- BIO
- Friedrich Miescher, Phoebus Levene
- PROBLEM
- Explore tetranucleotide combinations.
- LINKS
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One gene makes one protein.
(relating genes and protein function)
- CONCEPT
- Beadle and Tatum learn that mutations inactivate proteins.
- ANIMATION
- George Beadle and Edward Tatum present their experiments with Neurospora bread mold.
- GALLERY
- Beadle and neurospora
- VIDEO
- Joshua Lederberg
- BIO
- George Wells Beadle, Edward Lawrie Tatum
- PROBLEM
- Test understanding of synthesis pathways with mutant Neurospora.
- LINKS
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A gene is made of DNA.
(Oswald Avery: DNA as the transforming principle)
- CONCEPT
- Oswald Avery's team proves that DNA, not protein, is the genetic molecule.
- ANIMATION
- Oswald Avery explains Fred Griffith's and his own work with Pneumococcus bacteria.
- GALLERY
- Avery, MacLeod, and McCarty photos and correspondence
- VIDEO
- Maclyn McCarty
- BIO
- Oswald Theodore Avery, Maclyn McCarty
- PROBLEM
- Experiment with rough and smooth Pneumococcus DNA.
- LINKS
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Bacteria and viruses have DNA too.
(conjugation, Hershey and Chase experiment)
- CONCEPT
- Bacterial conjugation and bacteriophages provide proof that a gene is made of DNA.
- ANIMATION
- Joshua Lederberg worked with bacterial genetics while Alfred Hershey showed that DNA is responsible for the reproduction of new viruses in a cell.
- GALLERY
- Lederberg, Hershey, and Chase photos
- VIDEO
- Joshua Lederberg, Alfred Day Hershey
- BIO
- Joshua Lederberg, Alfred Day Hershey
- PROBLEM
- Understand bacterial conjugation.
- LINKS
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The DNA molecule is shaped like a twisted ladder.
(Watson and Crick: 3-D structure of DNA)
- CONCEPT
- Deoxyribose and phosphate molecules form the uprights and nucleotide pair form the rungs of the DNA ladder.
- ANIMATION
- James Watson and Francis Crick explain how they solved the structure of DNA. Erwin Chargaff explain how he measured the levels of each of the four nitrogenous bases.
- GALLERY
- Watson, Crick, and Chargaff photos
- VIDEO
- James Dewey Watson
- BIO
- James Watson, Francis Crick, Rosalind Franklin, Maurice Wilkins
- PROBLEM
- Explore DNA's structure.
- LINKS
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A half DNA ladder is a template for copying the whole.
(DNA replication)
- CONCEPT
- DNA polymerase and an experiment using nitrogen isotopes prove DNA replication.
- ANIMATION
- Matthew Meselson and Franklin Stahl show how new DNA is made by copying the old.
- GALLERY
- Delbruck, Stahl, Meselson and Kornberg photos
- VIDEO
- Frank Stahl, Matthew Meselson, Arthur Kornberg
- BIO
- Matthew Stanley Meselson, Franklin William Stahl, Arthur Kornberg
- PROBLEM
- Explore other theories on DNA replication.
- LINKS
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RNA is an intermediary between DNA and protein.
(RNA transcription, translation)
- CONCEPT
- The Central Dogma is the flow of genetic information from DNA, to RNA, to protein.
- ANIMATION
- Francis Crick describes RNA and its role and Paul Zamecnick explains protein synthesis.
- GALLERY
- Hoagland, Zamecnik, Brenner, and Benzer photos and documents
- VIDEO
- Paul Zamecnik
- BIO
- Paul Charles Zamecnik, Mahlon Hoagland, Sydney Brenner
- PROBLEM
- What happens in protein synthesis?
- LINKS
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DNA words are three letters long.
(genetic code, translation)
- CONCEPT
- Three DNA nucleotides form a codon and specifiy amino acids.
- ANIMATION
- Several researchers crack the genetic code.
- GALLERY
- Nirenberg, Leder, and Khorana photos
- VIDEO
- Marshall Nirenberg
- BIO
- Marshall Warren Nirenberg, Har Gobind Khorana
- PROBLEM
- Decode a protein.
- LINKS
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A gene is a discrete sequence of DNA nucleotides.
(DNA sequencing)
- CONCEPT
- Gene analysis take a giant leap using DNA sequencing.
- ANIMATION
- Fred Sanger outlines DNA sequencing.
- GALLERY
- Sanger photos
- VIDEO
- Richard McCombie
- BIO
- Frederick Sanger
- PROBLEM
- Determine the sequence of DNA.
- LINKS
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The RNA message is sometimes edited.
(RNA splicing, exons, introns)
- CONCEPT
- RNA splicing removes non-coding introns and splices together exons.
- ANIMATION
- Rich Roberts and Phil Sharp explain restriction enzymes, electrophoresis, and split genes.
- GALLERY
- Roberts, Chow, Broker, and Sharp photos
- VIDEO
- Richard Roberts, Phil Sharp
- BIO
- Richard John Roberts, Phillip Allen Sharp
- PROBLEM
- Map DNA molecules using restriction enzymes.
- LINKS
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Some viruses store genetic information in RNA.
(retroviruses, reverse transcriptase)
- CONCEPT
- Reverse transcription is found in retroviruses.
- ANIMATION
- David Baltimore and Howard Temin explain work on the Rous sarcoma virus.
- GALLERY
- Baltimore and Temin photos and HIV-1 virus electron micrographs
- VIDEO
- David Baltimore
- BIO
- David Baltimore, Howard Martin Temin
- PROBLEM
- Explore the reverse transcriptase mechanism.
- LINKS
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RNA was the first genetic molecule.
(RNA/DNA evolution)
- CONCEPT
- DNA is a more stable molecule that evolved from RNA.
- ANIMATION
- Stanley Miller and Harold Urey demonstrate that organic molecules can be synthesized under prebiotic conditions, and Thomas Cech and Sidney Altman show that RNA can have enzymatic activities.
- GALLERY
- Urey, Miller, Altman, and Cech photos
- VIDEO
- Raymond Gesteland
- BIO
- Stanley Lloyd Miller , Thomas Robert Cech
- PROBLEM
- Explore how RNA can self-splice.
- LINKS
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Mutations are changes in genetic information.
(DNA mutations)
- CONCEPT
- Some mutations are starting points for evolution, others are responsible for disease.
- ANIMATION
- Herman Muller induces fruit fly mutations. Seymour Benzer works with virus mutants ans proved only one nucleotide change can cause mutation.
- GALLERY
- Muller and Benzer photos
- VIDEO
- Elof Carlson, Svante Pääbo
- BIO
- Hermann Muller, Seymour Benzer
- PROBLEM
- Use mutations to measure human evolution.
- LINKS
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Some types of mutations are automatically repaired.
(DNA repair)
- CONCEPT
- DNA repair is central to survival.
- ANIMATION
- Stan Rupert explains UV damage and light-activated DNA repair systems and Richard Setlow's work on thymine dimer repair.
- GALLERY
- Herriott and Rupert photos
- VIDEO
- Richard Setlow, Jane Setlow
- BIO
- Claud S. Rupert, Richard B. Setlow
- PROBLEM
- Learn how the cause of Xeroderma pigmentosum is caused by a defect in a DNA repair system.
- LINKS
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Genetic Organization and Control
DNA is packaged in a chromosome.
(DNA packaging, chromatin)
- CONCEPT
- Each chromosome is a package for one very long, continuous strand of DNA.
- ANIMATION
- Roger Kornberg explains his work with Aaron Klug on histones, which bind DNA to form chromatin.
- GALLERY
- Kornberg, Klug, Hewish, and Burgoyne photos and chromatin micrographs
- VIDEO
- Roger Kornberg
- BIO
- Roger Kornberg
- PROBLEM
- Test your understanding of chromosome packaging.
- LINKS
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Higher cells incorporate an ancient chromosome.
(mitochondrial DNA)
- CONCEPT
- Mitochondria contain a circular genome molecule, tightly packed with genes.
- ANIMATION
- Ivan Wallin presents his idea that mitochondria and chloroplasts were once free-living organisms.
- GALLERY
- Wallin and cell micrograph
- VIDEO
- Svante Pääbo
- BIO
- Ivan Emanuel Wallin
- PROBLEM
- Trace mitochondria through Queen Victoria's decendents and solve the mystery of the Romanovs.
- LINKS
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Some DNA does not encode protein.
(non-coding, "junk" DNA)
- CONCEPT
- Long non-coding sequences separate relatively infrequent islands of genes in eukaryotic DNA.
- ANIMATION
- Roy Britten presents his work with David Kohne on repetitive DNA and its evolutionary origins.
- GALLERY
- Britten and mouse genome
- VIDEO
- Roy J. Britten
- BIO
- Roy John Britten
- PROBLEM
- Explore Britten's DNA reassociation rates for different organisms.
- LINKS
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Some DNA can jump.
(McClintock: "jumping" genes, transposons)
- CONCEPT
- Barbara McClintock showed that transposon DNA can be activated to jump to another position on a chromosome.
- ANIMATION
- Barbara McClintock presents her work with maize.
- GALLERY
- McClintock photos
- VIDEO
- Nathaniel Comfort
- BIO
- Barbara McClintock
- PROBLEM
- Explore other organisms with transposable elements.
- LINKS
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Genes can be turned on and off.
(lac operon, control of gene expression)
- CONCEPT
- Organisms can regulate gene expression.
- ANIMATION
- Jacques Monod and François Jacob work with how bacteria breaks large sugars into smaller pieces.
- GALLERY
- Jacob and Monod photos
- VIDEO
- Walter Gilbert
- BIO
- Jacques Lucien Monod, François Jacob
- PROBLEM
- Learn more about the lac operon system.
- LINKS
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Genes can be moved between species.
(DNA transformation, insulin production in bacteria)
- CONCEPT
- Recombinant DNA technology has made it possible to test gene function in bacteria or cell cultures rather than animal models.
- ANIMATION
- Stanley Cohen and Herbert Boyer transform bacteria with a recombinant plasmid, and Doug Hanahan studies induced transformation.
- GALLERY
- Boyer, Cohen, and Hanahan photos
- VIDEO
- Douglas Hanahan
- BIO
- Stanley Norman Cohen, Herbert W. Boyer, Douglas Hanahan
- PROBLEM
- Use green fluorescent protein to tag expression of genes.
- LINKS
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DNA responds to signals from outside the cell.
(cell signaling, interferon pathway)
- CONCEPT
- Signal transduction is cell communication that involves a series of molecular transformations.
- ANIMATION
- James Darnell explains how chemical signals turn eukaryotic genes on and off.
- GALLERY
- Darnell portrait
- VIDEO
- James E. Darnell, Jr.
- BIO
- James E. Darnell, Jr.
- PROBLEM
- Explore signal transduction.
- LINKS
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Different genes are active in different kinds of cells.
(gene expression, gene chip and DNA array technology)
- CONCEPT
- Cells differentiate because specific enzymes turn genes on and off in various cell types.
- ANIMATION
- Igor Dawid and Thomas Sargent explain how they developed subtractive mRNA hybrization to find genes expressed by different cell types. Pat Brown and Steve Fodor show how genomes can be screened with DNA arrays and GeneChip®.
- GALLERY
- Dawid, Sargent, Brown and Fodor photos
- VIDEO
- Tom Sargent, Patrick Brown
- BIO
- Igor Dawid, Thomas Dean Sargent, Patrick Henry Brown, Stephen P. A. Fodor
- PROBLEM
- Use DNA arrays to determine the best treatment for breast cancer.
- LINKS
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Master genes control basic body plans.
(fruit fly gene expression, development)
- CONCEPT
- Fruit fly mutaitons provided keys to understanding the molecular basis of large-scale developmental plans.
- ANIMATION
- Eric Wieschaus and Christiane Nüsslein-Volhard explain research of Drosophila's developmental stages, and Ed Lewis presents homeotic mutations.
- GALLERY
- Nüsslein-Volhard, Wieschaus, Lewis and Drosophila photos
- VIDEO
- Eric Wieschaus
- BIO
- Eric Francis Wieschaus, Christiane Nüsslein-Volhard, Edward Lewis
- PROBLEM
- Explore Drosophila development and embryonic protein distribution.
- LINKS
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Development balances cell growth and death.
(cell cycle, cell death)
- CONCEPT
- Normal development requires growth as well as apoptosis, or programmed cell death.
- ANIMATION
- Leland Hartwell describes how cells regulate the timing of growth and cell division. Bob Horvitz and Mike Hengartner explain control mechanisms for cell death.
- GALLERY
- Hartwell, Horvitz, Hengartner, and Lowe photos
- VIDEO
- Michael Hengartner, Cell death movie, Scott Lowe
- BIO
- Leland Hartwell, Howard Robert Horvitz, Michael Otmar Hengartner , Scott William Lowe
- PROBLEM
- Experiment with genes for cell death and survival in C. elegans.
- LINKS
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A genome is an entire set of genes.
(Human Genome Project)
- CONCEPT
- Our genome is a set of long DNA molecules containing tens of thousands of genes.
- ANIMATION
- James Watson describes sequencing the human genome using markers and BACs, and Craig Venter explains using cDNA libraries, ESTs, and shotgun sequencing.
- GALLERY
- Watson, Venter, and Collins photos
- VIDEO
- Francis S. Collins, J. Craig Venter
- BIO
- John Craig Venter, Francis Collins
- PROBLEM
- Locate a disease gene by screening for markers linked to the gene.
- LINKS
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Living things share common genes.
(DNA homology between species)
- CONCEPT
- All organisms store genetic information in DNA and RNA.
- ANIMATION
- Mike Wigler shows how all organisms share similar genes, called homologs.
- GALLERY
- Wigler, Varmus, and Bishop photos
- VIDEO
- Michael Wigler
- BIO
- Mike Wigler, John Michael Bishop, Harold Eliot Varmus
- PROBLEM
- Find a cystic fibrosis protein function using bioinformatics to study homologs in model organisms.
- LINKS
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DNA is only the beginning for understanding the human genome.
(gene targeting, proteomics)
- CONCEPT
- Discovering protein function is the next step in understanding the human genome.
- ANIMATION
- Mario Capecchi describes proteomics; the large-scale study of protein structure and function. Brian Sauer explains gene knock outs.
- GALLERY
- Capecchi and Sauer photos
- VIDEO
- Brian Sauer
- BIO
- Mario Renato Capecchi, Brian Sauer
- PROBLEM
- Experiment with gene knock outs.
- LINKS
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