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Glossary of AP Bio test 3

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Created by littledrummerboy

feedback inhibition
allows a cell to adapt to short-term fluctuations in the supply of a substance it needs by inhibiting the activity of enzymes
regulation of enzyme production
adjusts the amount of enzymes produced to adapt to long-term fluctuations in the supply of a substance it needs. this occurs at the level of transcription, the synthesis of mRNA coding for these enzymes
coordinate control
the ability to control a whole cluster of functionally related genes because they are in the same transcription unit and can be turned on or off with only one "switch"
operator
a segment of DNA that acts as a switch for a transcription unit, controlling the access of RNA polymerase to the genes. located within the promoter or between the promoter and the enzyme-coding genes
operon
the entire stretch of DNA that includes the operator, promoter, and the genes they control
repressor
a protein that can switch off an operon by binding to the operator and blocking the attachment of RNA polymerase to the promoter, preventing transcription oft he genes
regulatory gene
a gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes
corepressor
a small molecule that cooperates with a repressor protein to switch an operon off
inducer
a small molecule that inactivates a repressor by altering its confromation (changing its shape) to allow an operon to be transcribed into mRNA.
inducible operon
usually off but can be induced (turned on) when a specific small molecule (inducer) interacts with a regulatory protein (repressor)
inducible enzymes
enzymes with synthesis that is induced by a chemical signal
repressible enyzmes
enzymes with synthesis that can be repressed by a chemical signal
cyclic AMP (cAMP)
a small organic molecule made from ATP that is a common intracellular signaling molecule in eukaryotic cells (tells the cell about levels of a chemical like glucose within the cell). It is also a regulator of some bacterial operons
catabolite activator protein (CAP)
a regulatory protein that, when binded to cAMP, assumes its active shape and can attach to a specific site at the upstream end of a promotor
activator
a protein that binds to DNA and stimulates transcription of a gene
differential gene expression
the expression of different sets of genes by cells with the same genome
histone acetylation
the attachment of acetyl groups to certain amino acids of histone proteins. transcription proteins have easier access to genes in an acetylated region
genomic imprinting
a phenomenon in which expression of an allele is inherited from the male or female parent
epigenetic inheritance
inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence of a genome
control elements
segments of noncoding DNA that help regulate transcription by binding certain proteins
enhancers
groupings of distal control elements, control elements that are far from the promoter
mediator proteins
proteins that interact with other proteins, general transcription factors, at the promoter. these interactions help assemble and position the initiation complex on the promoter
transcription initiation complex
consists of the mediator proteins bound to the general transcription factors (other proteins) and the RNA polymerase II, which all interact at the promoter to speed up mRNA synthesis.
silencer
binds to the enhancer to reduce transcription
alternative RNA splicing
a type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns
mRNA degradation
mRNA will get eaten up by nuclease enzymes. if there is a longer poly-A tail, the message will not get destroyed as quickly. the length of the untranslated region (UTR) determines the lifespan of the message
proteasome
a giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin

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