A protein produced by B lymphocytes that binds to a foreign molecule.
antigen
A molecule against which an antibody is directed.
antisense nucleic acid
A nucleic acid (either RNA or DNA) that is complementary to an mRNA of interest and is used to block gene expression.
bacterial artificial chromosome (BAC)
A type of vector used for cloning large fragments of DNA in bacteria.
cDNA
A DNA molecule that is complementary to an mRNA molecule, synthesized in vitro by reverse transcriptase.
central dogma
The concept that genetic information flows from DNA to RNA to proteins.
chromosome
A carrier of genes, consisting of long DNA molecules and associated proteins.
codon
The basic unit of the genetic code; one of the 64 nucleotide triplets that code for an amino acid or stop sequence.
cosmid
A vector that contains bacteriophage λ sequences, antibiotic resistance sequences, and an origin of replication. It can accomodate large DNA inserts of up to 45 kb.
dideoxynucleotide
A nucleotide that lacks the normal 3′ hydroxyl group of deoxyribose and is used as a chain-terminating nucleotide in DNA sequencing.
diploid
An organism or cell that carries two copies of each chromosome.
DNA ligase
An enzyme that seals breaks in DNA strands.
DNA microarray
A glass slide or membrane filter onto which oligonucleotides or fragments of cDNAs are printed at a high density, allowing simultaneous analysis of thousands of genes by hybridization of the microarray with fluorescent probes.
DNA polymerase
An enzyme catalyzing the synthesis of DNA.
dominant
The allele that determines the phenotype of an organism when more than one allele is present.
dominant inhibitory mutant
A mutant that interferes with the function of the normal allele of the gene.
electroporation
The introduction of DNA into cells by exposure to a brief electric pulse.
embryonic stem (ES) cell
A stem cell cultured from an early embryo.
expression vector
A vector used to direct expression of a cloned DNA fragment in a host cell.
gel electrophoresis
A method in which molecules are separated based on their migration in an electric field.
gene
A segment of DNA that encodes a polypeptide chain or an RNA molecule.
gene transfer
The introduction of foreign DNA into a cell.
genetic code
The correspondence between nucleotide triplets and amino acids in proteins.
genotype
The genetic composition of an organism.
haploid
An organism or cell that has one copy of each chromosome.
homologous recombination
Recombination between segments of DNA with homologous nucleotide sequences.
immunoblotting
A method that uses antibodies to detect proteins separated by SDS-polyacrylamide gel electrophoresis.
immunoprecipitation
The use of antibodies to isolate proteins.
in situ hybridization
The use of radioactive or flourescent probes to detect RNA or DNA sequences in chromosomes or intact cells.
in vitro mutagenesis
The introduction of mutations into cloned DNA in vitro.
in vitro translation
Protein synthesis in a cell-free extract.
knockout
Inactivation of a chromosomal gene by homologous recombination with a cloned mutant allele.
liposome
A lipid vesicle used to introduce DNA into mammalian cells.
meiosis
The division of diploid cells to haploid progeny, consisting of two sequential rounds of nuclear and cellular division.
messenger RNA (mRNA)
An RNA molecule that serves as a template for protein synthesis.
molecular clone
See recombinant molecule.
molecular cloning
The insertion of a DNA fragment of interest into a DNA molecule (vector) that is capable of independent replication in a host cell.
monoclonal antibody
An antibody produced by a clonal line of B lymphocytes.
mutation
A genetic alteration.
Northern blotting
A method in which mRNAs are separated by gel electrophoresis and detected by hybridization with specific probes.
nucleic acid hybridization
The formation of double stranded DNA and/or RNA molecules by complementary base pairing.
one gene-one enzyme hypothesis
The hypothesis, based on analysis of nutritional mutants of Neurospora in the 1940s, that a gene specifies the structure of a single enzyme. The current statement of this hypothesis is that a gene specifies the structure of a single polypeptide chain.
origin of replication
A specific DNA sequence that serves as a binding site for proteins that initiate replication.
P1 artificial chromosome (PAC)
A vector used for cloning large fragments of DNA in E. coli.
phenotype
The physical appearance of an organism.
plasmid
A small, circular DNA molecule capable of independent replication in a host cell.
polymerase chain reaction (PCR)
A method for amplifying a region of DNA by repeated cycles of DNA synthesis in vitro.
recessive
An allele that is masked by a dominant allele.
recombinant DNA library
A collection of genomic or cDNA clones.
recombinant molecule
A DNA insert joined to a vector.
restriction endonuclease
An enzyme that cleaves DNA at a specific sequence.
restriction map
The locations of restriction endonuclease cleavage sites on a DNA molecule.
retrovirus
A virus that replicates by making a DNA copy of its RNA genome by reverse transcription.
reverse genetics
Analysis of gene function by introducing mutations into a cloned gene.
reverse transcriptase
A DNA polymerase that uses an RNA template.
reverse transcription
Synthesis of DNA from an RNA template.
ribosomal RNA (rRNA)
The RNA component of ribosomes.
RNA interference (RNAi)
The degradation of mRNAs by short complementary double-stranded RNA molecules.
RNA polymerase
An enzyme that catalyzes the synthesis of RNA.
SDS-polyacrylamide gel electrophoresis (SDS-PAGE)
A commonly used method to separate proteins by gel electrophoresis on the basis of size.
semiconservative replication
The process of DNA replication in which the two parental strands separate and serve as templates for the synthesis of new progeny strands.
Southern blotting
A method in which radioactive probes are used to detect specific DNA fragments that have been separated by gel electrophoresis.
temperature-sensitive mutant
A cell expressing a protein that is functional at one temperature but not at another, whereas the normal protein is functional at both temperatures.
Ti plasmid
A plasmid used for gene transfer in plants.
transcription
The synthesis of an RNA molecule from a DNA template.
transfection
The introduction of a foreign gene into eukaryotic cells.
transfer RNA (tRNA)
An RNA molecule that functions as an adaptor between amino acids and mRNA during protein synthesis.
transformation
The transfer of DNA between genetically distinct bacteria. See also cell transformation.
transgenic mouse
A mouse that carries foreign genes incorporated into the germ line.
transient expression
The expression of unintegrated plasmid DNAs that have been introduced into cultured cells.
translation
The synthesis of a polypeptide chain from an mRNA template.
vector
A DNA molecule used to direct the replication of a cloned DNA fragment in a host cell.
Western blotting
See immunoblotting.
yeast artificial chromosome (YAC)
A vector that can replicate as a chromosome in yeast cells and can accomodate very large DNA inserts (hundreds of kb).
yeast two-hybrid
A genetic method for detecting protein interactions in yeast cells.
