Essential Biology Chapter 10 Vocabulary

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Molecular biology

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The study of the molecular basis of heredity; molecular genetics.

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Nucleotides

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An organic monomer consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. Nucleotides are the building blocks of nucleic acids.

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Polynucleotide

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A polymer made up of many nucleotides covalently bonded together.

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Sugar-phosphate backbone

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

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DNA

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Deoxyribonucleic acid- The genetic material that organisms inherit from their parents; a double-stranded helical macromolecule consisting of nucleotide monomers with deoxyribose sugar, a phosphate group, and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T).

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Thymine (T)

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A single-ring nitrogenous base found in DNA.

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Cytosine (C)

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

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Adenine (A)

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

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Guanine (G)

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

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Uracil (U)

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A single-ring nitrogenous base found in RNA.

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Double helix

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The form assumed by DNA in living cells, referring to its two adjacent polynucleotide strands wound into a spiral shape.

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DNA polymerases

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An enzyme that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a template.

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Transcription

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The synthesis of RNA on a DNA template.

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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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Codons

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

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Genetic code

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The set of rules giving the correspondence between nucleotide triplets (codons) in mRNA and amino acids in proteins.

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RNA polymerase

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An enzyme that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template.

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Promoter

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A specific nucleotide sequence in DNA, located at the start of a gene, that is the binding site for RNA polymerase and the place where transcription begins.

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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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Messenger RNA (mRNA)

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The type of ribonucleic acid that encodes genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences.

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Cap

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Extra nucleotides added to the beginning of an RNA transcript in the nucleus of a eukaryotic cell.

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Tail

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Extra nucleotides added at the end of an RNA transcript in the nucleus of a eukaryotic cell.

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Introns

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In eukaryotes, a non-expressed (noncoding) portion of a gene that is excised from the RNA transcript.

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Exons

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In eukaryotes, a coding portion of a gene.

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RNA splicing

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The removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuous coding sequence; occurs before mRNA leaves the nucleus.

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Transfer RNA (tRNA)

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A type of ribonucleic acid that functions as an interpreter in translation. Each tRNA molecule has a specific anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA.

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Anticodon

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On a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA.

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Ribosomal (rRNA)

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The type of ribonucleic acid that, together with proteins, makes up ribosomes; the most abundant type of RNA.

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Start codon

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On mRNA, the specific three-nucleotide sequence (AUG) to which an initiator tRNA molecule binds, starting translation of genetic information.

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Codon recognition

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The anticodon of an incoming tRNA molecule, carrying its amino acid, pairs with the mRNA codon in the A site of the ribosome.

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Peptide bond formation

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The polypeptide leaves the tRNA in the P site and attaches to the amino acid on the tRNA in the A site. The ribosome catalyzes bond formation. Now the chain has one more amino acid.

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Translocation

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The P site tRNA now leaves the ribosome, and the ribosome moves the remaining tRNA, carrying the growing polypeptide, to the P site.The mRNA and tRNA move as a unit. This movement brings into the A site the next mRNA codon to be translated, and the process starts over.

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Stop codon

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

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Mutation

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A change in the nucleotide sequence of DNA; a major source of genetic diversity.

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Mutagens

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

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Virus

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A microscopic particle capable of infecting cells of living organisms and inserting its genetic material. Viruses have a very simple structure and are generally not considered to be alive because they do not display all of the characteristics associated with life.

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Bacteriophages

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A virus that infects bacteria; also called a phage.

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Lytic cycle

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A viral reproductive cycle resulting in the release of new viruses by lysis (breaking open) of the host cell.

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Lysogenic cycle

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A bacteriophage reproductive cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage. New phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome.

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Prophage

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Phage DNA that has inserted into the DNA of a prokaryotic chromosome.

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AIDS

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Acquired immunodeficiency syndrome; the late stages of HIV infection, characterized by a reduced number of T cells; usually results in death caused by opportunistic infections.

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HIV

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Human immunodeficiency virus; the retrovirus that attacks the human immune system and causes AIDS.

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Retrovirus

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An RNA virus that reproduces by means of a DNA molecule. It reverse-transcribes its RNA into DNA, , inserts the DNA into a cellular chromosome, then transcribes more copies of the RNA from the viral DNA. HIV and a number of cancer-causing viruses are retroviruses.

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Reverse transcriptase

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An enzyme that catalyzes the synthesis of DNA on an RNA template.

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Provirus

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Viral DNA that inserts into a host genome.

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Prions

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An infectious form of protein that may multiply by converting related proteins to more prions. Prions cause several related diseases in different animals, including scrapie in sheep, mad cow disease, and Creutzfeldt-Jakob disease in humans.

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Emerging viruses

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A virus that has appeared suddenly or has recently come to the attention of medical scientists.