Lodish 7E, Select Vocab, Chapter 5

Front 1

alleles

Back 1

one or two or more alternative forms of a gene; Diploid cells contain two alleles of each gene, located at the corresponding site (locus) on homologous chromosomes

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clone

Back 2

(1) population of genetically identical cells, viruses or organisms descended from a common ancestor. (2) multiple identical copies of a gene or DNA fragment generated and maintained via DNA Cloning

Front 3

complementary DNAs (cDNA

Back 3

DNA molecule copied from an mRNA molecule by reverse transcriptase and therefore lacking the introns present in the DNA of the genome

Front 4

DNA Cloning

Back 4

Recombinant DNA technique in which specific cDNAs or fragments of genomic DNA are inserted into a cloning vector, which then is incorporated into cultured host cells and maintained during growth of the host cells; also called gene cloning

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DNA Library

Back 5

Collection of cloned DNA molecules consisting of fragments of the entire genome (genomic library) or of DNA copies of all the mRNAs produced by a cell type (cDNA library) inserted into a suitable cloning vector

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DNA microarray

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an ordered set of thousands of different nucleotide sequences arrayed on a microscope slide or other solid surface; can be used to determine patterns of gene expression in different cell types or in a particular cell type at different developmental stages or under different conditions

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dominant

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in genetics, referring to that allele of a gene expressed in the phenotype of a heterozygote; the non-expressed allele is the recessive; also refers to the phenotype associated with a dominant allele; mutations that produce dominant alleles generally result in gain of function

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functional complementation

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procedures for screening a DNA library to identify the wild type gene that restores the function of a defective gene in a particular mutant

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gene knockout

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selective inactivation of a specific gene by replacing it with a nonfunctional (disrupted) allele in an otherwise normal organism

Front 10

genomics

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comparative analysis of the complete genomic sequences from different organisms and determination of global patterns of gene expression; used to assess evolutionary relations among species and to predict the number and general types of RNAs produced by an organism

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genotype

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entire genetic constitution of an individual cell or organism, usually with emphasis on particular alleles at one or more specific loci

Front 12

heterozygous

Back 12

referring to a diploid cell or organism having two different alleles of a particular gene

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homozygous

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referring to a diploid cell or organism having two identical alleles of a particular gene

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hybridization

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nucleic acid association of two complementary nucleic acid strands to form double stranded molecules, which can contain two DNA strands, two RNA strands, or one DNA and one RNA strand; used experimentally in various ways to detect specific DNA or RNA sequences

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linkage

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in genetics, the tendency of two different loci on the same chromosome to be inherited together; the closer the two loci are, the lower the frequency of recombination between them and the greater their linkage

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mutagen

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a chemical or physical agent that induces mutation

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mutation

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in genetics, a permanent, heritable change in the nucleotide sequence of a chromosome, usually in a single gene; commonly causes an alteration in the function of the gene product

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northern blotting

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technique for detecting specific RNAs separated by electrophoresis by hybridization to a labeled DNA probe

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phenotype

Back 19

the detectable physical and physiological characteristics of a cell organism determind by its genotype; also, the specific trait associated with a particular allele

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plasmids

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small, circular extra-chromosomal DNA molecule capable of autonomous replication in a cell; commonly used as a vector in DNA cloning

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point mutation

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change of a single nucleotide in DNA, especially in a region coding for protein; can result in formation of a codon specifying a different amino acid or a stop codon; addition or deletion of a single nucleotide will cause a shift in the reading frame

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polymerase chain reaction (PCR)

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technique for amplifying a specific DNA segment in a complex mixture by multiple cycles of DNA synthesis from short oligonucleotide primers followed by brief heat treatment to separate the complementary strands

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probes

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defined RNA or DNA fragment, radioactively, flourescently, or chemically labeled, that is used to detect specific nucleic acid sequences by hybridization

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recessive

Back 24

in genetics, referring to that allele of a gene that is not expressed in the phenotype when the dominant allele is present; also refers to the phenotype of an individual (homozygote) carrying two recessive alleles; mutations that produce recessive alleles generally result in a loss of the genes function

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recombinant DNA

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any DNA molecule formed in vitro by joining DNA fragments from different sources

Front 26

recombination

Back 26

any process in which chromosomes or DNA molecules are cleaved and the fragments are rejoined to give new combinations; homologous recombination occurs during meiosis, giving rise to crossing over of homologous chromosomes; homologous recombination and non-homologous chromosomes; homologous recombination and non-homologous recombination (i.e. between chromosomes of different morphological type) also occur during several DNA-repair mechanisms and can be carried out in vitro with purified DNA and enzymes

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restriction enzymes

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any enzyme that recognizes and cleaves a specific short sequence, the restriction site, in double stranded DNA molecules; used extensively to produce recombinant DNA in vitro; also called restriction endonuclease

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RNA interferance (RNAi)

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functional inactivation of a specific gene by corresponding double stranded RNA that induces either inhibition of translation or degradation of the complementary single stranded mRNA encoded by the gene but not that of mRNAs with a different sequence

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segregation

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the process that distributes an equal complement of chromosomes to daughter cells during mitosis and meiosis

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southern blotting

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technique for detecting specific DNA sequences separated by electrophoresis by hybridization to a labeled nucleic acid probe

Front 31

temperature sensitive mutations

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a temperature that produces a wild type phenotype at one temperature (the permissive temperature) but a mutant phenotype at another temperature (the non permissive temperature); this type of mutation is especially useful in identification of genes essential to life

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transfection

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experimental introduction of foreign DNA into cells in culture, usually followed by expression of genes in the introduced DNA

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transformation

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(1) permanent, heritable alteration in a cell resulting from the uptake and incorporation of a foreign DNA into the host cell genome; also called stable transfection. (2) conversion of a normal mammilian cell into a cell with cancer like properties usually induced by treatment with a virus or other cancer causing agent

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transgenes

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a cloned gene that is introduced and stably incorporated into a plant or animal and is passed on to successive generations

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vector

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in cell biology, an autonomously replicating genetic element used to carry a cDNA or fragment of genomic DNA into a host cell for the purpose of gene cloning; commonly used vectors are bacterial plasmids and modified bacteriophage genomes

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wild type

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normal non-mutant form of a gene, protein, cell, or organism

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Polylinkers

Back 37

Polylinkers are synthetic oligonucleotides composed of one copy of several different restriction sites. Plasmid vectors that contain a polylinker will be cut only once by multiple restriction enzymes, each acting at its own site. Inclusion of a polylinker in a plasmid vector thus permits cloning of restriction fragments generated by cleavage of DNA with multiple different restriction enzymes.

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E. coli Plasmids

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The most commonly used cloning vectors are E. coli plasmids, small circular DNA molecules that include three functional regions: (1) an origin of replication, (2) a drug-resistance gene, and (3) a region where DNA can be inserted without interfering with plasmid replication or expression of the drug-resistance gene.