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promoter
a site where RNA polymerase can bind to DNA and begin transcription
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operator
a switch for controlling transcription; positioned in the promoter or between the promoter and enzyme coding genes, it controls the access of RNA polymerase to the genes
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operon
the entire stretch of DNA required for enzyme production for an enzyme pathway; including the operator, the promoter, and the genes they control (ex: trp operon in E.coli)
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repressor
a protein that can turn of the operon; it binds to the operator and BLOCKS attachment of RNA polymerase to the promoter, preventing trasncription of the genes; the protein is specific for the operator of a particular operon
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regulatory gene
creates individual repressors; expressed continuously so there are always repressor molecules present
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corepressor
a small molecule that cooperates with a repressor protein to switch an operon off (if it binds to the repressor, the operon is turned off)
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inducer
present in the inducible operon (ex: in lac operon, allolactose) and is a small molecule that INACTIVATES the repressor
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cyclic amp
cAMP, a small organic molecule that accumulates when glucose is scarce
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activator
a protein that binds to DNA and stimulates transcription of a gene; ex: CAP
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differential gene expression
the expression of different genes by cells with the same genome, the cause of differences between cell types (ex: not due to different genes being present)
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histone acetylation
when acetyl groups are attached to lysines in the histone tails, neutralizing their positive charges and causing them to no longer bind to neighboring nucleosomes; this results in chromatin having a loser structure, and transcription proteins have easier access to the genes
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genomic imprinting
(in mammals) where methylation permanently regulates expression of either the maternal or paternal allele of particular genes at the start of development
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epigenetic inheritance
inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
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control elements
segments of noncoding DNA that help regulate transcription by binding certain proteins
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alternative RNA splicing
where different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns; regulatory proteins decide on intron/exon choices
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proteasomes
giant protein complexes that recogzine ubiquitin-tagged proteins and degrade them
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microRNAs
small single-stranded RNA molecules that are capable of binding to complementary sequences in mRNA molecules; when proteins attach and form a complex, it can either degrade target mRNA or block its translation
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RNA interference (RNAi)
when you inject double-stranded RNA molecules into a cell they turn off expression of a gene with the same sequence as the RNA
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small interfering RNAs (siRNAs)
similar to miRNAs except the difference is these are formed from longer double-stranded RNA molecules that give rise to MANY siRNAs; cause RNA interference (RNAi)
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cell differentiation
the process by which cells become specialized in structure and function; occurs during embryonic development
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morphogenesis
"creation of form", the physical process that give an organism its shape
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cytoplasmic determinants
maternal substances in the egg that influence the course of early development
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induction
signals such as from one embryonic cell to another as well as contact with cell-surface molecules on neighboring cells and the binding of growth factors secreted by neighboring cells that cause changes in the target cells
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determination
the events that lead to the observable differentiation of a cell; the outcome of determination is determinable cell differentiation; once a cell has undergone determination, an embryonic cell is irreversibly committed to it's final fate
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myoblasts
a type of embryonic progenitor cell that gives rise to myocytes, or muscle cells
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pattern formation
the process of cytoplasmic determinants and inductive signals dictating the organization of tissues and organs in their characteristic locations; spatial organizations in an organism
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positional information
the molecular cues that control pattern formation; controlled by cytoplasmic determinants and inductive signals
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homeotic genes
genes discovered by Edward B. Lewis in drosophila that control pattern formation in the late embryo, larvae and adult
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embryonic lethals
mutations in the phentotype that cause death at early stages of development (making them difficult to categorize/sequence)
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maternal effect gene
a gene that when mutant in the mother, results in a mutant phenotype in the offspring no matter WHAT the offspring's genotype is; also called egg-polarity genes
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bicoid
an embryo whose mother has a MUTANT bicoid gene lacks the front half of its body and has posterior structures at BOTH ends; means "two-tailed"
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morphogen gradient hypothesis
gradients of substances called morphogens establish an embryo's axes and other features of its form
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oncogenes
cancer causing genes; found in retroviruses
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proto-oncogenes
close counterparts of oncogenes that are found in the genomes of humans and other animals; they are the normal versions of the cellular genes and they code for proteins that stimulate NORMAL cell growth and division
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tumor-suppressor genes
genes whose normal products inhibit cell division; the proteins they encode help prevent uncontrolled cell growth
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ras gene
encodes the Ras protein which is a G protein that relays a signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases; the cellular response at the end of the pathway is the synthesis of a protein that stimulates the cell cycle
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p53 gene
tumor-suppressor gene; the protein it makes is a specific transcription factor that promotes the synthesis of cell cycle-inhibiting proteins (if knocked out, can cause uncontrolled growth)
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