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Biology LibreTexts


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  • A
    unitless spectrophotometer data; values are directly proportional to the concentration of a light-absorbing substance

    accession number

    unique identifier for a record in a database


    algal polysaccharides with gelling properties that are useful in preparing solid growth media for microorganisms

    agarose gel electrophoresis

    method for separating nucleic acids; because nucleic acids have a uniform negative charge, separation is primarily determined by size


    alternative forms of a gene

    amino acid

    monomeric subunit of proteins; a central carbon binds a proton, an amino group, a carboxyl group and a variable side chain known as the R (reactive) group


    binding of two single-stranded nucleic acids with complementary sequences; the double- stranded hybrid is stabilized by hydrogen bonds

    annotation (genome)
    process of analyzing genome sequences to identifying ORFs and functional elements


    an immunoglobulin; protein produced by B lymphocytes that binds a specific antigen with high affinity


    substances that stimulates the production of antibodies by lymphocytes


    chamber for sterilizing media and equipment using pressurized steam


    microorganism that has lost its ability to synthesize an essential nutrient due to a gene mutation


    virus that infects bacteria cells


    interdisciplinary research area concerned with the development of computational methods to analyze, store and access DNA and protein sequences


    process by which enzymes in living cells catalyze the synthesis of a biological molecule.


    base pair; lengths of DNA molecules are expressed in base pairs

    population of genetically identical cells that are descended from a single cell


    nonprotein component required by enzymes in order to function


    visible population containing hundreds of millions of gentically similar organisms, most likely descended from a single cell


    able to take up DNA from the environment


    restoration of a normal phenotype in a mutant cell by introduction of a gene that encodes a functional version of mutant gene product

    complementation group

    functional definition for a gene derived by studying collections of mutant organisms. Cells in the same complementation group carry mutations in the same gene.

    complex (molecular)
    association of molecules held together by noncovalent bonds


    professional who maintains and organizes records in databases


    glass or plastic sample holder used with a spectrophotometer


    organized collection of records, each of which has searchable fields

    treatment or agent, such as excessive heat, extreme pH, or chemical modification, that causes denaturation of proteins or nucleic acids


    destruction of native protein or nucleic acid structures, usually resulting in the loss of biological function


    organism with two copies of each chromo- some


    region/part of a protein that folds indepen- dently of other parts of the protein; domains are often functional units of a protein


    protein catalyst that accelerates the rate of a chemical reaction by lowering the activation energy


    portion of an antigen that binds an antibody

    Ffunctional genomics

    research area that studies the conservation of gene function during evolution

    fusion protein

    protein expressed from a genetically engineered plasmid that contains non-native functional elements at its N-terminus or C-terminus


    the entire DNA sequence of an organism


    the study of genomes, as opposed to individual genes


    the complete genetic makeup of an individual organism

    organism or cell containing only one set of chromosomes


    gene with high sequence similarity to another gene due to shared ancestry

    homologous recombination

    genetic recombination that normally occurs during meiosis; identical sequences on different DNA molecules align and initiate crossovers


    deliberate introduction of a microorganism into a medium that supports growth and reproduction

    intercalating agent

    chemical, such as ethidium bromide, that inserts into the DNA helix

    Llag phase

    growth period following inoculation of a liquid media, during which cells acclimate to the new environment and condition the media with their own metabolites

    log phase

    growth period where the number of cells increases exponentially


    immune cell that produces antibodies

    mixture of chemicals used to support the growth of microorganisms, generally in- cluding a carbon source, nitrogen source, salts, vitamins and essential minerals


    small prokaryote or eukaryote; visualiza- tion of individual microorganisms requires a microscope

    model organism

    organism that has been extensively studied in the laboratory for the insights it provides to higher eukaryotes; methods for genetic maniopulation are usually available; common model organisms include yeast, nematodes, fruit flies and zebrafish

    monoclonal antibody

    antibody binds to a defined epitope on an antigen. Monoclonal antibodies are produced by hybrid cell lines derived by fusing a lymphocyte with a meyloma cell.


    organism with a mutation in a gene of interest


    permanent change in a DNA sequence

    short, single-stranded polymer of nucleotides

    optical density

    spectrophotometer measurement of light scattering caused by suspensions of particles or cells

    ORF (open reading frame)

    potential protein coding sequence; stop codons are underrepresented in ORFs


    similar DNA sequences that have arisen from a common ancestral gene and are now found in different species


    similar sequences within the same genome; paralogs arise by gene duplicatiion events

    PCR (polymerase chain reaction)

    technique used to produce millions of copies of a DNA sequence of interst from a small number of template molecules


    observable physical properties of an organism


    small, circular DNA that replicates independently of thehost cell chromosomal DNA

    Rrecombinant DNA

    DNA molecule formed by combining segments of DNA from different sources; constructed by molecular biologists using enzymes such as polymerases, ligases and restriction endonucleases

    restriction digest

    incubation of DNA with a restriction endonuclease, which cleaves the DNA into a collection of fragments

    restriction endonuclease

    enzyme that cleaves DNA at a defined sequence of bases; also known as a restriction enzyme

    restriction map

    map of the restriction endonuclease recogni- tion sites in a length of DNA

    restriction site

    nucleotide sequence in a DNA molecule that is specifically recognized and cleaved by a restriction endonuclease

    R group

    side chain that distinguishes an amino acid; also known as the reactive group

    Sodium Dodecyl Sulfate-Polyacryamide GelElectrophoresis; the separation of proteins through a polyacrylamide gel matrix using an electic field

    selective medium

    growth medium that enhances the growth of some organisms, while preventing the growth of others, due to an added or absent media component


    group of organisms capable of breeding with each other and producing fertile descendants


    instrument that measures the amount of light absorbed by a sample at a particular wavelength

    stationary phase

    growth period that follows log phase and can be seen as a plateau in the growth curve, as cells begin to deplete available nutrients and growth rate slows

    strain (genetic)
    microorganisms of the same species that are descended from a single cell; members of the same strain have identical genotypes


    the liquid above the pellet after sedimenta- tion or centrifugation


    uptake of DNA from the environment, causing a change in a cell’s phenotype


    cell that has taken up DNA and expresses genes from the DNA, affecting its phenotype


    in molecular biology, a plasmid or virus used to transfer genes into a cell; usually a recombinant DNA constructed by molecular cloning


    rich, but undefined, media which supports yeast growth, consisting of Yeast extract,Peptone and Dextrose