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MBI 201- Exam 3
Chapters 7 and 8
54
Biology
Undergraduate 2
11/17/2007

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Term
Aminoacyl-tRNA synthetase
Definition
an enzyme that catalyzes attachment of an amino acid to its cognate tRNA
Term
Anticodon
Definition
a sequence of three bases in a tRNA molecule that base-pairs with a codon during protein synthesis
Term
Antiparallel
Definition
in reference to double-stranded DNA, one strand runs 5' --> 3' and the complementary strand 3' --> 5'
Term
Chromosome
Definition
a genetic element, usually circular in prokaryotes and linear in eukaryotes, carrying genes essential to cellular function
Term
Codon
Definition
a sequence of three bases in mRNA that encodes an amino acid
Term
Complementary
Definition
nucleic acid sequences that can base-pair with each other
Term
DNA gyrase
Definition
an enzyme found in most prokaryotes that introduces negative supercoils in DNA
Term
DNA Polymerase
Definition
an enzyme that synthesizes a new strand of DNA in the 5' -->3' direction using an antiparallel DNA strand as a template
Term
Exon
Definition
the coding DNA sequences in a split gene (in contrast with intron)
Term
Gene
Definition
a segment of DNA specifying a protein (via mRNA), a tRNA, or an rRNA
Term
Genome
Definition
the total complement of genes contained in a cell or virus
Term
Hybridization
Definition
formation of a duplex nucleic acid with strands derived from different sources by complementary base pairing
Term
Intron
Definition
the intervening noncoding DNA sequences in a split gene (contrast with exon)
Term
Messenger RNA (mRNA)
Definition
an RNA molecule that contains the genetic information to encode one or more polypeptides
Term
Molecular chaperone
Definition
a protein that helps other proteins fold or refold from a partially denatured state
Term
Operon
Definition
a cluster of genes whose expression is controlled by a single operator
Term
Polymerase chain reaction (PCR)
Definition
a method for the amplification of a specific DNA sequence in vitro by repeated cycles of synthesis using specific primers and DNA polymerase
Term
Primary transcript
Definition
an unprocessed RNA molecule that is the direct product of transcription
Term
Primer
Definition
an oligonucleotide to which DNA polymerase can attach the first deoxyribonucleotide during DNA replication
Term
Promoter
Definition
a site on DNA to which RNA polymerase binds to commence transcription
Term
Replication
Definition
synthesis of DNA using DNA as a template
Term
Restriction Enzyme
Definition
an enzyme that recognizes and breaks DNA at specific sequences
Term
Ribosomal RNA (rRNA)
Definition
types of RNA found in the ribosome; some participate actively in the process of protein synthesis
Term
Ribosome
Definition
a cytoplasmic particle composed of ribosomal RNA and protein whose function is to synthesize proteins
Term
RNA polymerase
Definition
an enzyme that synthesizes RNA in the 5' --> 3' direction using a complementary and antiparallel DNA strand as a template
Term
Semiconservative replication
Definition
DNA synthesis yielding new double helices, each consisting of one parental and one progeny strand
Term
Transcription
Definition
the synthesis of RNA using a DNA template
Term
Transfer RNA (tRNA)
Definition
an adaptor molecule used in translation that has specificity for both a particular amino acid and for one or more codons
Term
Translation
Definition
the synthesis of protein using the genetic information in messenger RNA as a template
Term
Activator protein
Definition
a regulatory protein that binds to specific sites on DNA and stimulates transcription involved in positive control
Term
Allosteric enzyme
Definition
an enzyme that contains two binding sites, the active site (where the substrate binds) and the allosteric site (where an effector molecule binds)
Term
Attenuation
Definition
a mechanism for controlling gene expression; typically transcription is terminated after initiation but before a full length mRNA is produced
Term
Feedback inhibition
Definition
a decrease in the activity of the first enzyme of a pathway caused by the final product of the pathway
Term
Gene expression
Definition
transcription and/or translation of genes
Term
Heat shock proteins
Definition
a series of proteins induced by a sudden upshift in temperature or certain other stress factors that function to refold partially denatured proteins
Term
Induction
Definition
production of an enzyme only when its substrate is present
Term
Kinase
Definition
an enzyme that adds a phosphoryl group to a compound
Term
Negative control
Definition
a mechanism for regulating gene expression in which a repressor protein functions to prevent transcription of a gene or genes
Term
Operon
Definition
one or more genes transcribed into a single RNA and under the control of a single regulatory site
Term
Positive control
Definition
a mechanism for regulating gene expression in which an activator protein functions to promote transcription of a gene or genes
Term
Quorum sensing
Definition
a regulatory system in an organism that require a certain density of cells of the same species be present before the regulatory events occur
Term
Repression
Definition
prevention of an enzymes synthesis when the product of its reaction is present in excess
Term
Repressor protein
Definition
a regulatory protein that binds to specific sites on DNA and blocks transcription; involved in negative control
Term
Response regulator protein
Definition
one of the members of a two-component system; a regulatory protein that is phosphorylated by a sensor kinase protein (see sensor kinase protein)
Term
Riboswitch
Definition
a messenger RNA that can bind a specific small molecule near its 5' end that alters its secondary structure and makes it unavailable for translation
Term
Sensor Kinase Protein
Definition
one of the members of a two-component system; a membrane-integrated protein that phosphorylates itself in response to an external signal and then transfers the phosphoryl group to a response regulator protein (see response regulator protein)
Term
Stringent Response
Definition
a global regulatory control that is activated by amino acid starvation
Term
Two-component regulatory system
Definition
a regulatory system containing two proteins: a sensor kinase and a response regulator (see sensor kinase protein and response regulator protein)
Term
Allosteric enzyme
Definition
has two binding sites, the active site (where the substrate binds) and the allosteric site (where the inhibitor (effector) binds reversibly
Term
isoenzyme
Definition
different proteins that catalyze the same reaction, but which are subject to different regulatory controls
Term
concerted feedback inhibition
Definition
each product feedback inhibits the enzyme's activity partially; complete inhibition occurs only when all three products are present in excess
Term
single-strand binding protein
Definition
stabiizes the single-stranded DNA after the helicase has unwinded the two strands at the replication fork
Term
Leading strand
Definition
strand growing from the 5' --> 3'
Continuously syntheisizing DNA because there is always a free 3'-OH at the replication fork to which a new nucleotide can be added
Term
Lagging strand
Definition
DNA synthesis occurs discontinuously because there is no 3'-OH at the replication form to which a new nucleotide can attach

RNA primer must be synthesized by primase multiple times to provide free 3'-OH groups
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