Exam 1 Vocab

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genes

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A hereditary determinant of a specifi c biological function;a unit of inheritance (DNA) located in a fixed position on a chromosome; a segment of DNA encoding one polypeptide anddefined operationally by the cis-trans or complementation test.

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alleles

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One of a pair, orseries, of alternative forms of a gene that occur at a given locus ina chromosome.

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nucleic acids

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A macromolecule composed of phosphoric acid, pentosesugar, and organic bases; DNA and RNA.

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nucleotides

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A subunit of DNA and RNA molecules containing aphosphate group, a sugar, and a nitrogen-containing organic base.

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ribonucleic acid (RNA)

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the information-carrying material in someviruses; more generally, a molecule derived from DNA by transcriptionthat may carry information (messenger or mRNA), providesubcellular structure (ribosomal or rRNA), transport aminoacids (transfer or tRNA), or facilitate the biochemical modificationof itself or other RNA molecules.

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deoxyribonucleic acid (DNA)

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Deoxyribonucleic acid; the information-carrying genetic materialthat comprises the genes. DNA is a macromolecule composedof a long chain of deoxyribonucleotides joined by phosphodiesterlinkages. Each deoxyribonucleotide contains a phosphate group, thefive-carbon sugar 2-deoxyribose, and a nitrogen-containing base.

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genome

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A complete set (n) of chromosomes (hence, of genes)inherited as a unit from one parent.

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Human Genome Project

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A huge international effort to map andsequence the entire human genome.

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genomics

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The study of the structure and function of entire genomes.

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polypeptides

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A linear molecule with two or more amino acids andone or more peptide groups. They are called dipeptides, tripeptides,and so on, according to the number of amino acids present.

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codons

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A set of three adjacent nucleotides in an mRNA moleculethat specifi es the incorporation of an amino acid into a polypeptidechain or that signals the end of polypeptide synthesis. Codonswith the latter function are called termination codons.

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transcription

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Process through which RNA is formed along a DNAtemplate. The enzyme RNA polymerase catalyzes the formationof RNA from ribonucleoside triphosphates.

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transcript

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The RNA molecule produced by transcription of a gene.

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messenger RNA (mRNA)

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RNA that carries information necessaryfor protein synthesis from the DNA to the ribosomes.

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translation

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Protein (polypeptide) synthesis directed by a specific messenger RNA; occurs on ribosomes.

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proteome

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The complete set of proteins encoded by a genome.

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proteomics

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The science focused on determining the structures andfunctions of all the proteins produced by living organisms.

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mutations

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A change in the DNA at a particular locus in an organism.The term is used loosely to include point mutations involving asingle gene change as well as a chromosomal change.

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phylogeny

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A diagram showing the evolutionary relationshipsamong a group of organisms; an evolutionary tree.

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cytoplasm

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The protoplasm of a cell outside the nucleus in whichcell organelles (mitochondria, plastids, and the like) reside; all livingparts of the cell except the nucleus.

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carbohydrate

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A molecule consisting of carbon, hydrogen, and oxygenin the proportions 1:2:1; a molecule of sugar or a macromoleculecomposed of sugar subunits.

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lipids

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A molecule composed of fatty acids and triglycerides.

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Proteins

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A macromolecule composed of one to several polypeptides.Each polypeptide consists of a chain of amino acids linked togetherby peptide bonds.

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enzymes

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A protein that accelerates a specific chemical reaction in aliving system.

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nucleic acids

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A macromolecule composed of phosphoric acid, pentosesugar, and organic bases; DNA and RNA.

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plasmids

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An extrachromosomal hereditary determinant that exists inan autonomous state and is transferred independently of chromosomes.

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diploid

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An organism or cell with two sets of chromosomes (2n) ortwo genomes. Somatic tissues of higher plants and animals areordinarily diploid in chromosome constitution in contrast withthe haploid (monoploid) gametes.

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somatic cell

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A cell that is a component of the body, in contrast witha germ cell that is capable, when fertilized, of reproducing theorganism.

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gametes

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A mature male or female reproductive cell (sperm or egg).

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haploid

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An organism or cell having only one completeset (n) of chromosomes or one genome.

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germ line

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The tissue that ultimately produces the gametes.

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centromere

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Spindle fiber attachment region of a chromosome.

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clone

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All the individuals derived by vegetative propagation from asingle original individual. In molecular biology, a population ofidentical DNA molecules all carrying a particular DNA sequencefrom an organism.

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mother cell

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A cell that is prepared to divide mitotically or meiotically.

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daughter cells

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A product of cell division.

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fission

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A mode of cell division among the prokaryotes in which thegenetic material of the mother cell is fi rst duplicated and thenapportioned equally to the two daughter cells.

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colony

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A compact collection of cells produced by the division of asingle progenitor cell.

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cell cycle

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The cyclical events that occur during the divisions ofmitotic cells. The cell cycle oscillates between mitosis and theinterphase, which is divided into G1, S, and G2.

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mitosis

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Disjunction of duplicated chromosomes and division of thecytoplasm to produce two genetically identical daughter cells.

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cytokinesis

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Cytoplasmic division and other changes exclusive ofnuclear division that are a part of mitosis or meiosis.

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chromatin

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The complex of DNA and proteins in eukaryotic chromosomes;originally named because of the readiness with which itstains with certain dyes.

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interphase

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The stage in the cell cycle when the cell is not dividing;the metabolic stage during which DNA replication occurs; thestage following telophase of one division and extending to thebeginning of prophase in the next division.

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sister chromatids

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One of the products of chromosome duplication.

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microtubules

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Hollow fi laments in the cytoplasm making up a partof the locomotor apparatus of a motile cell; component of themitotic spindle.

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spindle

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A system of microtubules that distributes duplicated chromosomesequally and exactly to each of the daughters of a dividingeukaryotic cell.

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microtubule organizing center (MTOC)

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A region in a eukaryoticcell that generates the microtubules used during cell division.In animal cells, the MTOC is associated with distinct organellescalled centrosomes.

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centrosomes

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A barrel-shaped organelle associated with the mitoticspindle in animal cells.

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centrioles

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An organelle in many animal cells that appears to beinvolved in the formation of the spindle during mitosis.

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aster

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the sunburst pattern that the daughter centrosomes form into - microtubules form around them

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prophase

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The stage of mitosis between interphase and metaphase.During this phase, the centriole divides and the two daughter centriolesmove apart. Each sister DNA strand from interphase replicationbecomes coiled, and the chromosome is longitudinallydouble except in the region of the centromere. Each partially separatedchromosome is called a chromatid. The two chromatids ofa chromosome are sister chromatids.

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nucleolus

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An RNA-rich, spherical sack in the nucleus of metaboliccells; associated with the nucleolar organizer; storage place forribosomes and ribosome precursors.

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kinetochores

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A proteinaceous structure associated with the centromereof a chromosome during eukaryotic cell division; the point atwhich microtubules attach to move the chromosome through thedivision process.

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metaphase

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That stage of cell division in which the chromosomesare most discrete and arranged in an equatorial plate; stage followingprophase and preceding anaphase.

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metaphase plate

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The equatorial plane where duplicated chromosomesgather in a cell during the metaphase of mitosis.

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anaphase

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The stage of mitosis or meiosis during which the daughterchromosomes pass from the equatorial plate to opposite polesof the cell (toward the ends of the spindle). Anaphase followsmetaphase and precedes telophase.

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telophase

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The last stage in each mitotic or meiotic division in whichthe chromosomes are assembled at the poles of the division spindle.

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meiosis

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The process by which the chromosome number of a reproductivecell becomes reduced to half the diploid (2n) or somaticnumber; results in the formation of gametes in animals or of sporesin plants; important source of variability through recombination.

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homologues

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Chromosomes that occur in pairs andare generally similar in size and shape, one having come from themale parent and the other from the female parent. Such chromosomescontain the same array of genes.

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heterologues

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A chromosome that contains a differentset of genes than the chromosome to which it is compared.

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prophase I

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The stage during the fi rst meiotic division when duplicatedchromosomes condense and pair with their homologues.

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leptonema

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Stage in meiosis immediately precedingsynapsis in which the chromosomes appear as single, fi ne,threadlike structures (but they are really double because DNAreplication has already taken place).

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zygonema

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Stage in meiosis during which synapsisoccurs; after the leptotene stage and before the pachytene stage inthe meiotic prophase.

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synapsis

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The pairing of homologous chromosomes in the meioticprophase.

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synaptinemal complex

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A ribbonlike structure formed betweensynapsed homologues at the end of the fi rst meiotic prophase,binding the chromatids along their length and facilitating chromatidexchange.

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pachynema

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A mid-prophase stage in meiosisimmediately following zygonema and preceding diplonema. Infavorable microscopic preparations, the chromosomes are visibleas long, paired threads. Rarely, four chromatids are detectable.

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bivalent

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A pair of synapsed or associated homologous chromosomesthat have undergone the duplication process to form a group offour chromatids.

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tetrad

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The four cells arising from the second meiotic division inplants (pollen tetrads) or fungi (ascospores). The term is also usedto identify the quadruple group of chromatids that is formed bythe association of duplicated homologous chromosomes duringmeiosis.

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crossing over

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A process in which chromosomes exchange materialthrough the breakage and reunion of their DNA molecules.

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diplonema

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That stage in prophase of meiosis Ifollowing the pachytene stage, but preceding diakinesis, in whichthe chromosomes of bivalents separate from each other at andaround their centromeres.

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chiasmata

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A visible change of partners in two ofa group of four chromatids during the fi rst meiotic prophase. Inthe diplotene stage of meiosis, the four chromatids of a bivalentare associated in pairs, but in such a way that one part of twochromatids is exchanged. This point of “change of partner” is thechiasma.

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diakinesis

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A stage of meiosis just before metaphase I in which thebivalents are shortened and thickened.

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metaphase I

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The stage during the fi rst meiotic division when duplicatedhomologous chromosomes that have paired condense andgather at the equatorial plane of the cell.

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anaphase I

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The stage during the fi rst meiotic division when duplicatedhomologous chromosomes separate from each other andbegin moving to opposite poles of the cell.

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telophase I

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The stage during the fi rst meiotic division when duplicatedchromosomes gather at the pole of a dividing cell and beginto decondense.

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prophase II

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The stage during the second meiotic division whenduplicated chromosomes condense and prepare to move to theequatorial plane of the cell.

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metaphase II

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The stage during the second meiotic division whenduplicated chromosomes gather at the equatorial plane of the cell.

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anaphase II

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The stage during the second meiotic division when sisterchromatids of a duplicated chromosome separate from eachother and begin moving to opposite poles of the cell.

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telophase II

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The stage during the second meiotic division whenthe chromosomes gather at the pole of a dividing cell and begin todecondense.

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model organisms

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Plants, animals, and microbes that are routinelyused in genetic analysis.

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anthers

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The organ in fl owers that produces pollen.

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stamens

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The elongated structure that bears the anthers in fl oweringplants.

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ovary

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The swollen part of the pistil of a plant fl ower that containsthe ovules; the female reproductive organ or gonad in animals.

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pistil

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The centrally located organ in fl owers that contains the ovary.

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microspores

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One of the four end products of meiosis in the malereproductive tissues of plants.

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megaspores

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The single large cell produced at the end of meiosis inthe female reproductive tissues of plants.

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sporophyte

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The diploid generation in the life cycle of a plant thatproduces haploid spores by meiosis.

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pollen grain

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The male gametophyte in higher plants.

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male gametophyte

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The three identical haploid nuclei within a pollengrain.

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embryo sac

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A large thin-walled space within the ovule of the seedplant in which the egg and, after fertilization, the embryo develop;the mature female gametophyte in higher plants.

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female gametophyte

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A large thin-walled space within the ovule ofthe seed plant that contains the eight identical haploid nuclei derivedby mitosis from the megaspore that was produced by meiosis.

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gametogenesis

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The formation of gametes.