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210 A, Ch 18
N/A
47
Biology
Undergraduate 1
04/29/2012

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Term
Operator
Definition
In bacterial and phage DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach. The binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon
Term
Operon
Definition
A unit of genetic function found in bacteria and phage DNA, consisting of a promoter, an operator, and a coodinately regulated cluster of genes whose products function in a common pathway.
Term
Repressor
Definition
The repressor binds to the operator and blocks the attachment of RNA polymerase to the promoter, which prevents transcription of that gene. (a repressor is a protein)... The binding of a repressor is reversible... It is only in active form (with can bind to promoter) if it has a specific ligand bound to its active site, so if that ligand is not there then it is in the inactive form.
Term
Regulatory gene
Definition
A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes
Term
Corepressor
Definition
A small molecule that cooperates with a repressor protein to switch an operon off.
Term
Repressible operon
Definition
Transcription is usually "on" but can be inhibited when a specific small molecule binds allosterically to a regulatory protein
Term
Inducible operon
Definition
Transcription is usually "off" but can be stimulated when a specific small molecule interacts with a regulatory protein.
Term
Inducer
Definition
A specific small molecule that binds to a bacterial repressor protein and changes the repressors shape so that it cannot bind to an operator, thus switching an operon ON
Term
Negative control of genes
Definition
The operons are switched off by the active form of the repressor protein.
Term
Positive control of genes
Definition
When a regulatory protein interacts directly with the genome to switch transcription on.
Term
Activator
Definition
A protein that binds to DNA and stimulates transcription of a gene
Term
Differential gene expression
Definition
The expression of different genes by cells with the same genome.
Term
Histone acetylation
Definition
acetyl groups are attached to lysines in histone tails...(deacetylation is the removal of acetyl groups, this is referred to as "silencing" the gene)... when lysines are acetylated, their positive charge is nuetralized, and histone tails no longer interact with neighboring nucleosomes. When this happens, transcription proteins can more readily attach to genes in the acetylated region
Term
Histone code hypthesis
Definition
Specific combinations of modifications, as well as the order in which they have occured, help determine the chromatin configuration, which in turn influences transcription.
Term
DNA methylation
Definition
The presence on methyl groups on the DNA bases (usually cytosine) of plants, animals and fungi... In general, areas that are not transcribed tend to be more methylated than regions that are frequently transcribed... Thus the removal of methyl groups can lead to certain genes being "turned on.".... can be used for Genomic imprinting in mammals.
Term
Epigenetic inheritance
Definition
Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
Term
Control elements
Definition
Segments of noncoding DNA that serve as binding sites for the proteins called transcription factors, which in turn regulate transcription
Term
General transcription factors
Definition
Transcription factors that are essential for the transciption of all protein coding genes.
Term
Specific transcription factors
Definition
In eukaryotes, high levels of transcription of particular genes at the appropriate time and place depend on the interaction of control elements with another set of proteins, which can be thought of as specific transcription factors.
Term
Enhancers
Definition
A segment of eukaryotic DNA containing multiple control elements, usually located far from the gene whose transcription it regulates... A gene may have multiple enhancers, each active at a different time or in a different cell type or location in the organism... Each enhancer is generall associated with only that gene and no other.
Term
Transcription Factories
Definition
Areas of the nucleus where loops of different chromosomes can interact with each other... tend to be rich with RNA polymerases and other transcription associated proteins... are thought to be areas specialized for a common function.
Term
mRNA degradation
Definition
in bacteria, it tends to be quite fast, usually a few minutes... In eukaryotes, mRNA can last hours, days and even weeks... Amount of time that mRNA remains intact correlates with the length of the untranslated region (UTR) at the 3' end.
Term
Initiation of translation regulation
Definition
Translation can be blocked by regulatory proteins that bind to the 5' or 3' UTR.
Term
Proteasomes
Definition
A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin
Term
ncRNA
Definition
noncoding RNA... it is functinal RNA that is not translated to a protein.
Term
miRNA
Definition
microRNA... small single stranded RNA molecules... capable of binding to complementary sequences in mRNA molecules... miRNA are formed from longer RNA precursors that fold back on themselves, forming one or more double stranded hairpin structures, each held together by hydrogen bonds. Each hairpin is cut away from the precursor and trimmer by an enzyme (Dicer), into short double stranded fragments 22 nucleotides pairs. One strand in degraded and the other strand (miRNA), the miRNA forms a complex with a protein... This complex can bind to any mRNA that has a 7-8 nucleotide complementary sequence. The complex may then degrade the mRNA or block it for translation
Term
RNAi
Definition
RNA interference...A technique used to silence the expression of genes. RNAi uses synthetic double stranded RNA molecules that match the sequence of a particular gene to trigger the breakdown of the gene's mRNA.
Term
siRNA
Definition
small interfering RNA...One of multiple small, single stranded RNA molecules generated by cellular machinery from a long linear, double stranded RNA molecule. The siRNA associates with one or more proteins in a complex that can degrade or prevent translation of mRNA with a complementary sequences. In some cases, siRNA can also block transcription by promoting chromatin modification
Term
piwiassociated RNAs
Definition
piRNAs... induce the formation of heterochromatin, blocking the expression of some parasitic DNA elements in the genome known as transposons... piRNA are usually 24-31 nucleotides long, they play a role in gamete formation, by re-establishing methylation patterns in the genome during gamete formation.
Term
The three processes that give rise of a zygote and the organism it becomes?
Definition
Cell division (mitosis), cell differentiation, and morphohenesis
Term
Cell differentiation
Definition
The process by which cells become specialized in structure and function.
Term
Morphogenesis
Definition
The cellular and tissue based processes by which an animal body takes shape.
Term
Cytoplasmic determinants
Definition
Maternal substances in the egg that influence the course of early development.... the cytoplasm is not homogeneous, so when the zygote begins to separate into different cells, the nuclei are exposed to different cytoplasmic determinants
Term
Induction
Definition
The process in which one group of embryonic cells influence the development of another, usually by causing changes in gene expression
Term
Determination
Definition
The progressive restriction of development potential in which the possible fate of each cell becomes more limited as an embryo develops. At the end of determination, a cell is committed to its fate
Term
Pattern Formation
Definition
The development of a multicellular organism's spatial organization, the arrangement of organs and tissues in their characteristic places in three dimensional space... cytoplasmic determinants and inductive signals both contribute to pattern formation.
Term
Positional information
Definition
The molecular cues that control pattern formation... are provided by cytoplasmic determinants and inductive signals
Term
homeotic genes
Definition
The genes that control pattern formation in the late embyo, larva and adult.
Term
Embryonic lethals
Definition
Mutations with phenotypes causing death at the embryonic or larval stage.
Term
Maternal effect gene
Definition
Is a gene that, when mutant in the mother, results in a mutant phenotype in the offspring regardless of the offsprings own genotype... Also called egg-polarity genes
Term
Bicoid
Definition
A maternal effect gene that codes for a protein responsible for specifying the anterior end in Drosophilia... causes offspring to have two tails
Term
Morphogens
Definition
A substance that provides positional information in the form of a concentraion gradient along the embryonic axis.
Term
Oncognes
Definition
Cancer causing genes in certain types of viruses
Term
proto-oncogenes
Definition
The normal versions of cellular genes that code for proteins that stimulate normal cell growth and division
Term
Tumor-suppressor genes
Definition
The proteins they encode help prevent uncontrolled cell growth.
Term
ras gene
Definition
(rat sarcoma, a connective tissue in cancer)... Is a G protein that relays a signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases
Term
p53
Definition
is a tumor suppressor gene... named for the 53,000-dalton molecular weight of it protein product
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