Dna&protein Synthesis

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adenine

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(A) A double-ring nitrogenous base found in DNA and RNA.

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AIDS

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(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.

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anticodon

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A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.

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bacterial chromosome

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The single, circular DNA molecule found in bacteria

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bacteriophage

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A virus that infects bacteria; also called a phage. See phage.

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codon

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A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

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cytosine

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(C) A single-ring nitrogenous base found in DNA and RNA.

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DNA ligase

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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

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DNA polymerase

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An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.

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double helix

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The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.

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exon

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A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns.

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genetic code

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genetic code
The set of rules relating nucleotide sequence to amino acid sequence.

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guanine

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guanine
(G) A double-ring nitrogenous base found in DNA and RNA.

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HIV

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HIV
(human immunodeficiency virus)The infectious agent that causes AIDS; HIV is an RNA retrovirus.

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intron

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intron
A noncoding, intervening sequence within a eukaryotic gene.

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lysogenic cycle

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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.

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lytic cycle

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lytic cycle
A type of viral replication cycle resulting in the release of new phages by death or lysis of the host cell.

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mutagen

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A chemical or physical agent that interacts with DNA and causes a mutation.

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mutation

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A rare change in the DNA of a gene ultimately creating genetic diversity.

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nucleotide

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The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

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peptide bond

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The covalent bond between two amino acid units, formed by a dehydration reaction.

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polynucleotide

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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.

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promoter

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A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.

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prophage

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A phage genome that has been inserted into a specific site on the bacterial chromosome.

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provirus

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Viral DNA that inserts into a host genome.

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reading frame

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The way a cell’s mRNA-translating machinery groups the mRNA nucleotides into codons

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retrovirus

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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

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reverse transcriptase

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An enzyme encoded by some RNA viruses that uses RNA as a template for DNA synthesis

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ribosomal RNA

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(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.

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RNA polymerase

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An enzyme that links together the growing chain of ribonucleotides during transcription.

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RNA splicing

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The removal of noncoding portions (introns) of the RNA molecule after initial synthesis.

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stop codon

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In mRNA, one of three triplets (UAG, UAA, UGA) that signal gene translation to stop.

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sugar-phosphate backbone

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The alternating chain of sugar and phosphate to which the DNA and RNA nitrogenous bases are attached.

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terminator

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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.

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thymine

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(T) A single-ring nitrogenous base found in DNA.

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transcription

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The synthesis of RNA on a DNA template

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transfer RNA

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(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.

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translation

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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.

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uracil

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(U) A single-ring nitrogenous base found in RNA.