Chapter 9 Genetics Vocabulary

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Gene regulation

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processes by which gene expression is controlled in response to external or internal signals

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coordinate regulation

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control of synthesis of several proteins by a single regulatory element; in prokaryotes, the proteins are usually translated from a single mRNA molecule

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negative regulation

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regulation of gene expression in which mRNA is not synthesized until a repressor is removed from the DNA of the gene

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repressor

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a protein that binds specifically to a regulatory sequence adjacent to a gene and blocks transciption of the gene

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inducible transcription

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transcription of a gene or a group of genes, only in the presence of an inducer molecule

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inducer

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a small molecule that inactivates a repressor, usually by binding to it and thereby altering the ability of the repressor to bind to an operator.

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repressible transcription

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a regulatory process in which a gene is temporarily rendered unable to be transcribed

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aporepressor

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a protein converted into a repressor by binding with a particular molecule

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co-repressor

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a small molecule that binds with an aporepressor to create a functional repressor molecule

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Beta galactosidase

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an enzyme that cleave lactose into its glucose and galactose constituents; produced by a gene in the lac operon

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lactose premease

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an enzyme responsible for transport of lactose from the environment into bacteria

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constitutive mutant

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a mutant in which synthesis of a particular mRNA molecule and the protein it encodes, takes place at a constant rate independent of the presence or absence of any inducer or repressor molecule

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cis-dominant

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pertaining ot a mutation that affects the expression of only those genes on the same DNA molecule

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operator

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a regulatory region in DNA that intereacts with a specific repressor protein in controlling the transcription of adjacent structural genes

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promoter

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a dna sequence at which rna polymerase binds and initiate transcription

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lactose operon model

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6 steps

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operon

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a collection of adjacent structural genes regulated by an operator and a repressor

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cAMP-CRP

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a regulatory complex consisting of cyclic AMP (cAMP) and the CAP protein; the complex is needed for transcription of certain operons

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attenuation

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transcriptional regulatation that is exerted based on the concentration of charged tryptophan tRNA

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attenuator

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a regulatory base sequence near the beginning of an mRNA molecule at which transcription can be terminated; when an attenuator is present, it precedes the coding sequences

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leader polypeptide

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as short polypeptide encoded in the leader sequence of some operons coding for enzymes in amino acid biosynthesis; translation of the leader polypeptide participates in regulation of the operon through attenuation.

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riboswitch

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a 5' RNA leader sequence that, according to whether it is bound with a small molecule, can adopt either of two configurations, one of which permits transcription and the other of which terminates transcription

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housekeeping genes

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a gene that is experessed at the same level in virtually all cells and whose product participates in basic metabolic processes

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enhancers

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a base sequence in eukaryotes and eukaryotic viruses that increases the rate of transcription of nearby genes; the defining characteristics are that it need not be adjacent to the trancribed gene and that the enhancing activity is independent of orientation with respect to the gene

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silencers

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a nucleotide sequence that binds with certain proteins whose presence prevents gene expression

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transcription complex

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an aggregate of RNA polymerase (consisting of its own subunits) along with other polypeptide subunits that makes transcription possible

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DNA looping

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a mechanism by which enhancers that are distant ifrom the immediate proximity of a promoter can still regulate transcription; the enhancer and promoter, both bound with suitable protein factors, come into indirect physical contact by menas of the looping out of the DNA between them. The physical interactiion simulates transcription

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basal transcription factors

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transcription factors that are associated with transcription of awide variety of genes

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general transcription factors

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a protein molecule needed to bind with a promoter before transcription can proceed; transcription factors are necessary, but not sufficient, for transcription, and they ar e shared among many different promoters

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TATA-box-binding protein (TBP)

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a protein that binds to the TATA motif in the promoter region fo a gene

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TBP-associated factors (TAFs)

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any protein found in close association with TATA binding protein

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Pol II holoenzyme

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a large protein complex containing th etype of RNA polymerase used in transcribing most protein encoding genes

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chromatin-remodeling complexes (CRCs)

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any of a number of complex protein aggregates that reorganizes the nucleosomes of chromatin in prepration for transcription

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epigenetic

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heritable changes in gene expression due to something "in addition to" the DNA sequence, usually either chemical modification of the bases or protein factors bound with the DNA

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DNA methylase

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man enzyme that adds methyl groups to certain bases particularly cytosine

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genomic imprinting

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a process of DNA modifiaction in gametogenesis that affects gene expression in a zygote; one probable mechanism is the methylation of certain bases in the DNA

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RNA interference (RNAi)

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the ability of small fragments of double-stranded RNA to silence gen3es whose transcripts contain homologous sequences

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antisense RNA

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an RNA molecule complementary in nucleotide sequence to all or part of a messenger RNA

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variable antibody regions

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the portion of an immunoglobulin molecule that varies greatly in amino acid sequence among antibodies in the same subclass

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constant antibody regions

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the part of the heavy and light chains of an antibody molecule that has the same amino acid sequence among all antibodies derived from the same heavychain and ligh-chain genes

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variable antibody regions

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the portion of an immunoglobulin molecule that varies greatly in amino acid sequence among antibodies in the same subclass

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joining antibody regions

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any of multiple dna sequences that code for alternative amino acid sequences of an antibody molecule; the J regions of heavy and light chains are different

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v-j joining

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DNA splicing that unites on of the V regions of an antibody light-chain gene with one of the J (joining) regions of the same gene to create a unique antibody sequence

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constant (C) antibody region

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the part of the heavy and light chains of an antibody molecule that has the same amino acid sequence among all antibodyies derived from the same heavy chain and light-chain genes.

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mating-type interconversion

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phenomenon in homothallic yeast in which cells switch mating type as a result of the transposition of genetic information from an unexpressed cassette into the active mating-type locus

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homothallism

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the capacity of cells in certain fungi to undergo a conversino in mating type to make possible mating between cells produced by the same parental organism

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Positive regulation

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Mechanism of gene regulation in which an element must be bound to DNA in an active form to allow transcription; contrasts with negative regulation, in which a regulatory element must be removed from DNA

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Transcriptional activator protein

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positive control element that stimulates transcription by binding with particular sites in DNA

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Autoregulation

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Regulation of gene expression by the product of the gene itself

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Prader-Willi Syndrome

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A rare spontaneous deletion inluding chromosme region 15q11 that takes place in the father

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Angelman Syndrome

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A rare spontaneous deletion inluding chromosme region 15q11 that takes place in the mother