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Biology HESI
HESI Standardized Test
| Question | Answer |
|---|---|
| aerobe | a microorganism that grows in the presence of oxygen |
| amino acid | any of 20 basic building blocks of proteins. |
| anaerobe | a microorganism that grows in the absence of oxygen |
| antibiotic resistance | the ability of a microorganism to produce a protein to disable an antibiotic or prevents transport of the antibiotic into the cell |
| antibiotic | a class of natural and synthetic compounds that inhibit the growth or kill other microorganisms |
| Antibody. | An immunoglobulin protein produced by B- lymphocytes of the immune system that binds to a specific antigen molecule. |
| Anticodon. | A nucleotide base triplet in a transfer RNA molecule that pairs with a complementary base triplet, or codon, in a messenger RNA molecule. |
| Antigen. | Any foreign substance, such as a virus, bacterium, or protein, that elicits an immune response by stimulating the production of antibodies. |
| Antigenic determinant. | A surface feature of a microorganism or macromolecule, such as a glycoprotein, that elicits an immune response. |
| Antimicrobial agent. | Any chemical or biological agent that harms the growth of microorganisms. |
| Asexual reproduction. | Nonsexual means of reproduction which can include grafting and budding. |
| Autosome | A chromosome that is not involved in sex de- termination. |
| Bacillus. | A rod-shaped bacterium. |
| Backcross. | Crossing an organism with one of its parent organisms. |
| Bacteriocide. | A class of antibiotics that kills bacterial cells. |
| Bacteriophage (phage or phage particle). | A virus that infects bacteria. Altered forms are used as vectors for cloning DNA. |
| Bacterioostat. | A class of antibiotics that prevents growth of bacterial cells. |
| Bacterium. | A single-celled, microscopic prokaryotic organism: a single cell organism without a distinct nucleus. |
| Base pair (bp). | A pair of complementary nitrogenous bases in a DNA molecule--adeninethymine and guanine-cytosine. Also, the unit of measurement for DNA sequences. |
| Biologics. | Agents, such as vaccines, that give immunity to diseases or harmful biotic stresses. |
| Catalyst. | A substance that promotes a chemical reaction by lowering the activation energy of a chemical reaction, but which itself remains unaltered at the end of the reaction. |
| Catalytic antibody (abzyme). | An antibody selected for its ability to catalyze a chemical reaction by binding to and stabilizing the transition state intermediate. |
| Catalytic RNA (ribozyme). | A natural or synthetic RNA molecule that cuts an RNA substrate. |
| Cation. | A positively charged ion. |
| Centers of origin. | Usually the location in the world where the oldest cultivation of a particular crop has been identified. |
| Centromere. | The central portion of the chromosome to which the spindle fibers attach during mitotic and meiotic division. |
| Chemotherapy. | A treatment for cancers that involves administering chemicals toxic to malignant cells. |
| Chloramphenicol. | An antibiotic that interferes with protein synthesis. |
| Chromatid. | Each of the two daughter strands of a duplicated chromosome joined at the centromere during mitosis and meiosis. |
| Codon. | A group of three nucleotides that specifies addition of one of the 20 amino acids during translation of an mRNA into a polypeptide. Strings of codons form genes and strings of genes form chromosomes. |
| Coenzyme | a vitamin, that binds to an enzyme and is required for its catalytic activity. |
| Colony. | A group of identical cells (clones) derived from a single progenitor cell. |
| Conjugation. | The joining of two bacteria cells when genetic material is transferred from one |
| bacterium to another. | |
| Cross-hybridization. | The hydrogen bonding of a single- stranded DNA sequence that is partially but not entirely complementary to a single-stranded substrate. Often, this involves hybridizing a DNA probe for a specific DNA sequence to the homologous sequences of different spe |
| Crossing-over. | The exchange of DNA sequences between chromatids of homologous chromosomes during meiosis. |
| Cross-pollination. | Fertilization of a plant from a plant with a different genetic makeup. |
| Culture. | A particular kind of organism growing in a laboratory medium. |
| Dalton. | A unit of measurement equal to the mass of a hydrogen atom, 1.67 x 10E-24 gram/L (Avogadro's number). |
| Death phase. | The final growth phase, during which nutrients have been depleted and cell number decreases. |
| Denature. | To induce structural alterations that disrupt the biological activity of a molecule. Often refers to breaking hydrogen bonds between base pairs in double-stranded nucleic acid molecules to produce in single-stranded polynucleotides or altering the second |
| Density gradient centrifugation | High-speed centrifugation in which molecules "float" at a point where their density equals that in a gradient of cesium chloride or sucrose. |
| Dideoxynucleotide (didN). | A deoxynucleotide that lacks a 3' hydroxyl group, and is thus unable to form a 3'-5' phosphodiester bond necessary for chain elongation.Dideoxynucleotides are used in DNA sequencing and the treatment of viral diseases |
| carcinogen | a substance that induces cancer |
| carcinoma | a malignant tumor derived from epithelial tissue, which forms the skin and outer layers of internal organs |
| Diploid cell. | A cell which contains two copies of each chromosome. |
| DNA (Deoxyribonucleic acid). | An organic acid and polymer composed of four nitrogenous bases--adenine, thymine, cytosine, and guanine linked via intervening units of phosphate and the pentose sugar deoxyribose. DNA is the genetic material of most organisms and usually exists as a doub |
| DNA sequencing. | Procedures for determining the nucleotide sequence of a DNA fragment. |
| Dominant gene. | A gene whose phenotype is when it is present in a single copy. |
| Dominant(-acting) oncogene. | A gene that stimulates cell proliferation and contributes to oncogenesis when present in a single copy. |
| Dominant. | An allele is said to be dominant if it expresses its phenotype even in the presence of a recessive allele. |
| Dormancy. | A period in which a plant does not grow, awaiting necessary environmental conditions such as temperature, moisture, nutrient availability. |
| Double helix. | Describes the coiling of the antiparallel strands of the DNA molecule, resembling a spiral staircase in which the paired bases form the steps and the sugar-phosphate backbones form the rails. |
| Double-stranded complementary DNA (dscDNA). | A duplex DNA molecule copied from a cDNA template. |
| Ecology. | The study of the interactions of organisms with their environment and with each other. |
| Ecosystem. | The organisms in a plant population and the biotic and abiotic factors which impact on them. See abiotic factors; Biotic factors. |
| Electrophoresis. | The technique of separating charged molecules in a matrix to which is applied an electrical field. |
| Electroporation. | A method for transforrning DNA, especially useful for plant cells, in which high voltage pulses of electricity are used to open pores in cell membranes, through which foreign DNA can pass. |
| Endophyte. | An organism that lives inside another. |
| Enzymes. | Proteins that control the various steps in all chemical reactions. |
| Eukaryote. | An organism whose cells possess a nucleus and other membrane-bound vesicles, including all members of the protist, fungi, plant and animal kingdoms; and excluding viruses, bacteria, and blue-green algae. |
| Evolution. | The long-term process through which a population of organisms accumulates genetic changes that enable its members to successfully adapt to environmental conditions and to better exploit food resources. |
| Flanking region. | The DNA sequences extending on either side of a specific locus or gene. |
| Fungus. | A microorganism that lacks chlorophyll. |
| Gene insertion. | The addition of one or more copies of a normal gene into a defective chromosome. |
| Gene. | A locus on a chromosome that encodes a specific protein or several related proteins. It is considered the functional unit of heredity. |
| Genetic engineering. | The manipulation of an organism's genetic endowment by introducing or eliminating specific genes through modern molecular biology techniques. A broad definition of genetic engineering also includes selective breeding and other means of artificial selecti |
| Genetic marker. | A gene or group of genes used to "mark" or track the action of microbes. |
| Genotype. | The structure of DNA that determines the expression of a trait. |
| Genus. | A category including closely related species. Interbreeding between organisms within the same category can occur. |
| Growth factor. | A serum protein that stimulates cell division when it binds to its cell-surface receptor. |
| Haploid cell. | A cell containing only one set, or half the usual (diploid) number, of chromosomes. |
| Hemophilia. | An X-linked recessive genetic disease, caused by a mutation in the gene for clotting factor VIII (hemophilia A) or clotting factor IX (hemophilia B), which leads to abnormal blood clotting. |
| Homologous chromosomes. | Chromosomes that have the same linear arrangement of genes-a pair of matching chromosomes in a diploid organism. |
| Homologous recombination. | The exchange of DNA fragments between two DNA molecules or chromatids of paired chromosomes (during crossing over) at the site of identical nucleotide sequences. |
| Host. | An organism that contains another organism. |
| Hydrogen bond. | A relatively weak bond formed between y. a hydrogen atom (which is covalently bound to a nitrogen or oxygen atom) and a nitrogen or oxygen with an unshared electron pair |
| Hydrolysis. | A reaction in which a molecule of water is added at the site of cleavage of a molecule to two products. |
| In situ. | Refers to performing assays or manipulations with intact tissues. |
| In vivo. | Refers to biological processes that take place within a living organism or cell. |
| Incomplete dominance. | A condition where a heterozygous off- spring has a phenotype that is distinctly different from, and intermediate to, the parental phenotypes. |
| Insulin. | A peptide hormone secreted by the islets of Langerhans of the pancreas that regulates the level of sugar in the blood. |
| Interferon. | A family of small proteins that stimulate viral resistance in cells. |
| Lysis. | The destruction of the cell membrane. |
| Malignant. | Having the properties of cancerous growth. |
| Meiosis. | The reduction division process by which haploid gametes and spores are formed, consisting of a single duplication of the genetic material followed by two mitotic divisions. |
| Messenger RNA (mRNA). | The class of RNA molecules that copies the genetic information from DNA, in the nucleus, and carries it to ribosomes, in the cytoplasm, where it is translated into protein. |
| Metabolism. | The biochemical processes that sustain a living cell or organism. |
| Mitosis. | The replication of a cell to form two daughter cells with identical sets of chromosomes. |
| Molecular biology. | The study of the biochemical and molecular interactions within living cells. |
| Mutagen. | Any agent or process that can cause mutations. |
| Mutation. | An alteration in DNA structure or sequence of a gene. |
| Natural selection. | The differential survival and reproduction of organisms with genetic characteristics that enable them to better utilize environmental resources. |
| Nucleic acids. | The two nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are made up of long chains of molecules called nucleotides. Nucleotide. A building block of DNA and RNA, consisting of a nitrogenous base, a five-carbon sugar, and a phosphate |
| Occupational Safety and Health Administration (OSHA). | One of the U.S. agencies responsible for regulation of biotechnology. The major law under which the agency has regulatory powers is the Occupational Safety and Health Act. |
| Organelle. | A cell structure that carries out a specialized function in the life of a cell. |
| Ovum. | A female gamete. |
| Parasitism. | The closest association of two or more dissimilar organisms where the association is harmful to at least one. |
| Pathogen. | Organism which can cause disease in another organism. |
| Persistence. | Ability of an organism to remain in a particular setting for a period of time after it is introduced. |
| Pesticide. | A substance that kills harmful organisms (for example, an insecticide or fungicide). |
| Phenotype. | The observable characteristics of an organism, the expression of gene alleles (genotype) as an observable physical or biochemical trait. |
| Phospholipid. | A class of lipid molecules in which a phosphate group is linked to glycerol and two fatty acyl groups. A chief component of biological membranes. |
| Plaque. | A clear spot on a lawn of bacteria or cultured cells where cells have been Iysed by viral infection. |
| Polymer. | A molecule composed of repeated subunits. |
| Polypeptide (protein). | A polymer composed of multiple amino acid units linked by peptide bonds. |
| Polysaccharide. | A polymer composed of multiple units of monosaccharide (simple sugar). |
| Primary cell. | A cell or cell line taken directly from a living organism, which is not immortalized. |
| Prokaryote. | A bacterial cell lacking a true nucleus; its DNA is usually in one long strand. |
| Protease. | An enzyme that cleaves peptide bonds that link amino acids in protein molecules. |
| Protein kinase. | An enzyme that adds phosphate groups to a protein molecule at serine, threonine, or tyrosine residues. |
| Protein. | A polymer of amino acids linked via peptide bonds and which may be composed of two or more polypeptide chains |
| Recessive gene. | Characterized as having a phenotype expressed only when both copies of the gene are mutated or missing |
| Recombinant DNA. | The process of cutting and recombining DNA fragments from different sources as a means to isolate genes or to alter their structure and function. |
| Recombinant. | A cell that results from recombination of genes. |
| Retrovirus. | A member of a class of RNA viruses that utilizes the enzyme reverse transcriptase to reverse copy its genome into a DNA intermediate, which integrates into the hostcell chromosome. Many naturally occurring cancers of vertebrate animals are caused by retr |
| Reverse genetics. | Using linkage analysis and polymorphic markers to isolate a disease gene in the absence of a known metabolic defect, then using the DNA sequence of the cloned gene to predict the amino acid sequence of its encoded protein. |
| Ribosomal RNA (rRNA). | The RNA component of the ribosome. |
| RNA (ribonucleic acid). | An organic acid composed of repeating nucleotide units of adenine,bonds. |
| Sexual reproduction. | The process where two cells (gametes) fuse to form one hybrid, fertilized cell. |
| Subunit vaccine. | A vaccine composed of a purified antigenic determinant that is separated from the virulent organism. |
| Synapsis. | The pairing of homologous chromosome pairs during prophase of the first |
| meiotic division, when crossing over occurs. | |
| Taq polymerase. | A heat-stable DNA polymerase isolated from the bacterium Therrnus aquaticus, used in PCR. |
| Telomere. | The end of a chromosome. |
| Transcription. | The process of creating a complementary RNA copy of DNA. |
| Vaccine. | A preparation of dead or weakened pathogen, or of derived antigenic determinants, that is used to induce formation of antibodies or immunity against the pathogen. |
| Vector. | An autonomously replicating DNA molecule into which foreign DNA fragments are inserted and then propagated in a host cell. Also living carriers of genetic material (such as pollen) from plant to plant, such as insects. |
| Virulence. | The degree of ability of an organism to cause disease. |
| Virus. | An infectious particle composed of a protein capsule and a nucleic acid core, which is dependent on a host organism for replication. A double-stranded DNA copy of an RNA virus genome that is integrated into the host chromosome during lysogenic infection. |
| Wild type. | An organism as found in nature; the organism before it is genetically engineered. |
| X-linked disease. | A genetic disease caused by a mutation on the X chromosome. In X-linked recessive conditions, a normal female "carrier" passes on the mutated X chromosome to an affected son. |
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