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allele One of two or more alternative forms of a gene that exist at a specific gene location on a chromosome.

amino acid The fundamental chemical subunit of proteins. There are 20 common amino acids.

bacteriophage A virus that infects bacteria. Also called a phage.

chromosomes Long thread-like structures made of DNA and protein that are the gene-bearing structures of eukaryotic cells.

codon A three-nucleotide sequence that codes for a specific amino acid or a stop signal in protein synthesis.

denaturation A process in which a protein's structure is altered, causing the protein to become biologically inactive.

deoxyribonucleic acid (DNA) A double-stranded, helical nucleic acid molecule that is the carrier of genetic information.

DNA ligase An enzyme that can join nucleotides in a DNA strand.

DNA replication The copying of a DNA molecule.

DNA sequencing The process of deciphering the precise order of nucleotide bases in a DNA molecule.

electrophoresis The separation and identification of molecules based on their movement through an electrically charged field.

enol form A form of guanine or thymine in which a hydrogen atom bonds to a nearby oxygen atom that sticks out from the nitrogen ring of the base.

enzymes A class of proteins that act as catalysts, chemical agents that change the rate of a reaction without being consumed by the reaction.

gene A discrete unit of hereditary information that is located on the chromosomes and consists of DNA.

gene cloning The process of synthesizing multiple copies of a particular DNA sequence using a bacterial cell or another organism as a host.

genetic code The set of sixty-four codons corresponding to each of the 20 amino acids.

genetic engineering The technique of altering the genetic makeup of cells or organisms by deliberately inserting, removing, or altering individual genes.

heterozygous Having two different alleles for a given trait.

helix Having a spiral, coiled form such as a screw thread or a spring.

isomers Molecules with the same chemical composition but with different chemical structures.

keto form A form of guanine or thymine in which a hydrogen atom bonds to a nitrogen atom within the nitrogen ring of the base.

nitrogenous base One of four nitrogen containing bases - adenine, thymine, guanine, and cytosine - that make up nucleotides.

nucleic acid An acid compound, such as DNA or RNA, that is found in the nucleus of a cell.

nucleotides A chemical subunit composed of a five-carbon sugar, bonded to a phosphate group and nitrogenous base, which makes up the nucleic acids.

plasmids A circular, self-replicating form of DNA found in many species of bacteria. Plasmids can sometimes be used as a vector to transfer recombinant genes into another species.

protein A molecular chain containing amino acid subunits linked together in a specific sequence.

purines One of two families of nitrogenous bases found in nucleotides. Two members are adenine and guanine.

pyrimidines One of two families of nitrogenous bases found in nucleotides. Two members are cytosine and thymine.

recombinant DNA (rDNA) A DNA sequence produced artificially by joining pieces of DNA from different organisms.

restriction enzyme An enzyme that cuts DNA molecules at a specific base sequence.

RNA A single-stranded nucleic acid involved in protein synthesis. The structure of RNA is determined by DNA.

tautomers Two or more isomers which have a different placement of a hydrogen atom and can exist in equilibrium.

vector A plasmid, virus, or other vehicle that is used to move a recombinant DNA sequence into the cell of another organism.

X-ray crystallography A technique that involves the use of X-ray photographs to study the arrangement of atoms, ions, or molecules in substances.


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