Chapter 18/19 Flashcards
activator
A protein that binds to DNA and stimulates gene transcription. In prokaryotes, activators bind in or near the promoter; in eukaryotes, activators generally bind to control elements in enhancers.
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.
bicoid
A maternal effect gene that codes for a protein responsible for specifying the anterior end in Drosophila melanogaster.
control element
A segment of noncoding DNA that helps regulate transcription of a gene by serving as a binding site for a transcription factor. Multiple control elements are present in a eukaryotic gene’s enhancer.
corepressor
A small molecule that binds to a bacterial repressor protein and changes the protein’s shape, allowing it to bind to the operator and switch an operon off.
cyclic AMP (cAMP)
Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells. It is also a regulator of some bacterial operons.
cytoplasmic determinant
A maternal substance, such as a protein or RNA, that when placed into an egg influences the course of early development by regulating the expression of genes that affect the developmental fate of cells.
determination
The progressive restriction of developmental 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.
differential gene expression
The expression of different sets of genes by cells with the same genome.
differentiation
The process by which a cell or group of cells becomes specialized in structure and function.
DNA methylation
The presence of methyl groups on the DNA bases (usually cytosine) of plants, animals, and fungi. (The term also refers to the process of adding methyl groups to DNA bases.)
embryonic lethal
A mutation with a phenotype leading to death of an embryo or larva.
enhancer
A segment of eukaryotic DNA containing multiple control elements, usually located far from the gene whose transcription it regulates.
epigenetic inheritance
Inheritance of traits transmitted by mechanisms that do not involve the nucleotide sequence.
histone acetylation
The attachment of acetyl groups to certain amino acids of histone proteins.
homeotic gene
Any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells.
inducer
A specific small molecule that binds to a bacterial repressor protein and changes the repressor’s shape so that it cannot bind to an operator, thus switching an operon on.
induction
A process in which a group of cells or tissues influences the development of another group through close-range interactions.
long noncoding RNA (lncRNA)
An RNA between 200 and hundreds of thousands of nucleotides in length that does not code for protein but is expressed at significant levels.
maternal effect gene
A gene that, when mutant in the mother, results in a mutant phenotype in the offspring, regardless of the offspring’s genotype. Maternal effect genes, also called egg-polarity genes, were first identified in Drosophila melanogaster.
microRNA (miRNA)
A small, single-stranded RNA molecule, generated from a double-stranded RNA precursor. The miRNA associates with one or more proteins in a complex that can degrade or prevent translation of an mRNA with a complementary sequence.
morphogen
A substance, such as Bicoid protein in Drosophila, that provides positional information in the form of a concentration gradient along an embryonic axis.
morphogenesis
The development of the form of an organism and its structures.
oncogene
A gene found in viral or cellular genomes that is involved in triggering molecular events that can lead to cancer.
operator
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.
operon
A unit of genetic function found in bacteria and phages, consisting of a promoter, an operator, and a coordinately regulated cluster of genes whose products function in a common pathway.
p53 gene
A tumor-suppressor gene that codes for a specific transcription factor that promotes the synthesis of proteins that inhibit the cell cycle.
pattern formation
The development of a multicellular organism’s spatial organization, the arrangement of organs and tissues in their characteristic places in three-dimensional space.
positional information
Molecular cues that control pattern formation in an animal or plant embryonic structure by indicating a cell’s location relative to the organism’s body axes. These cues elicit a response by genes that regulate development.
proto-oncogene
A normal cellular gene that has the potential to become an oncogene.
ras gene
A gene that codes for Ras, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases, ultimately resulting in stimulation of the cell cycle.
regulatory gene
A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.
repressor
A protein that inhibits gene transcription. In prokaryotes, repressors bind to the DNA in or near the promoter. In eukaryotes, repressors may bind to control elements within enhancers, to activators, or to other proteins in a way that blocks activators from binding to DNA.
RNA interference (RNAi)
A mechanism for silencing the expression of specific genes. In RNAi, double-stranded RNA molecules that match the sequence of a particular gene are processed into siRNAs that either block translation or trigger the degradation of the gene’s messenger RNA. This happens naturally in some cells, and can be carried out in laboratory experiments as well.
small interfering RNA (siRNA)
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 an mRNA with a complementary sequence.
tumor-suppressor gene
A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.
