Molecular Basis of Genetics Vocabulary

adenine
A double-ring nitrogenous base found in DNA and RNA.
AIDS
(acquired immunodeficiency syndrome)The name of the late stages of HIV infection; defined by a specified reduction of T cells and the appearance of characteristic secondary infections.
anticodon
A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
bacterial chromosome
The single, circular DNA molecule found in bacteria.
bacteriophage
A virus that infects bacteria; also called a phage. See phage.
codon
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
cytosine
A single-ring nitrogenous base found in DNA and RNA
deoxyribonucleic acid
(DNA) A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell's proteins.
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.
DNA polymerase
An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.
double helix
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape
exon
A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns.
genetic code
The set of rules relating nucleotide sequence to amino acid sequence.
guanine
A double-ring nitrogenous base found in DNA and RNA.
HIV
(human immunodeficiency virus)The infectious agent that causes AIDS; HIV is an RNA retrovirus.
intron
A noncoding, intervening sequence within a eukaryotic gene.
lysogenic cycle
A phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host
lytic cycle
A type of viral replication cycle resulting in the release of new phages by death or lysis of the host cell.
messenger RNA
(mRNA) A type of RNA synthesized from DNA, that attaches to ribosomes and specifes the primary structure of proteins.
mutagen
A chemical or physical agent that interacts with DNA and causes a mutation.
mutation
A rare change in the DNA of a gene ultimately creating genetic diversity
nucleotide
The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group
peptide bond
The covalent bond between two amino acid units, formed by a dehydration reaction.
phage
A virus that infects bacteria; also called a bacteriophage.
polynucleotide
A polymer consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA
prophage
A phage genome that has been inserted into a specific site on the bacterial chromosome
provirus
Viral DNA that inserts into a host genome.
reading frame
The way a cellís mRNA-translating machinery groups the mRNA nucleotides into codons.
retrovirus
An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.
reverse transcriptase
An enzyme encoded by some RNA viruses that uses RNA as a template for DNA synthesis.
ribonucleic acid
(RNA) A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses.
ribosomal RNA
(rRNA) The most abundant type of RNA, which together with proteins, forms the structure of ribosomes. Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons.
RNA polymerase
An enzyme that links together the growing chain of ribonucleotides during transcription.
RNA splicing
The removal of noncoding portions (introns) of the RNA molecule after initial synthesis.
stop codon
In mRNA, one of three triplets (UAG, UAA, UGA) that signal gene translation to stop.
sugar-phosphate backbone
The alternating chain of sugar and phosphate to which the DNA and RNA nitrogenous bases are attached.
terminator
A special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene
thymine
A single-ring nitrogenous base found in DNA.
transcription
The synthesis of RNA on a DNA template.
transfer RNA
(tRNA) An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
translation
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of "language" from nucleotides to amino acids.
translocation
An aberration in chromosome structure resulting from an error in meiosis or from mutagens; specifically, attachment of a chromosomal fragment to a nonhomologous chromosome.
uracil
A single-ring nitrogenous base found in RNA.