Ergito: Life Sciences Glossary R

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R segment: The R segments are the sequences that are repeated at the ends of a retroviral RNA. They are called R-U5 and U3-R.
Defined as key term in
Molecular Biology—Essentials 4.22.4 Viral DNA is generated by reverse transcription
Molecular Biology 4.17.4 Viral DNA is generated by reverse transcription
r-protein: An r-protein is one of the proteins of the ribosome.
Defined as key term in
Molecular Biology 3.11.11 r-protein synthesis is controlled by autogenous regulation
r-strategist: r-strategist is a species for which the intrinsic rate of population increase (rmax) is very high, resulting in opportunistic growth and unstable population size.
Defined as key term in
Introduction to Biology 2.6.5 Species adopt different growth strategies to exploit their environments
Rab: Rab proteins are small Ras-like GTPases. Different Rabs are required for protein trafficking between different membrane compartments. Although their exact role is not clear, Rabs appear to regulate membrane targeting and fusion.
Defined as key term in
Cell Biology 2.4.11 Rabs and tethers are two types of proteins that regulate vesicle targeting
Cell Biology 2.4.4 Concepts in vesicle-mediated protein transport
Molecular Biology 6.27.8 The exocyst tethers vesicles by interacting with a Rab
Rab effector: Rab effectors are proteins that bind to the GTP-bound form of Rabs and help to carry out their function(s).
Defined as key term in
Cell Biology 2.4.11 Rabs and tethers are two types of proteins that regulate vesicle targeting
Radiant energy: Radiant energy is energy that arrives on the Earth from the Sun.
Defined as key term in
Introduction to Biology 2.2.7 Energy from the Sun warms Earth and is radiated back into space
Radiation hybrid mapping: Radiation hybrid mapping is a type of genetic mapping providing resolution between relatively low-resolution linkage analysis and high-resolution physical mapping by the assembly of contiguous cloned DNA segments.
Defined as key term in
Genetics 2.11.27 Supplemental section: Radiation hybrids provide a form of physical mapping
Radioisotope: A radioisotope is an unstable form of an isotope. It spontaneously decays, giving off high energy atomic particles.
Defined as key term in
Introduction to Biology 2.3.3 Tectonic plate movements create earthquakes, volcanoes, and repositioning of continents
Rain shadow: A rain shadow is an area on one side of a mountain that receives little precipitation.
Defined as key term in
Introduction to Biology 2.4.6 Arid conditions create deserts and chaparrals
Random drift: Random drift describes the chance fluctuation (without selective pressure) of the levels of two alleles in a population.
Defined as key term in
Molecular Biology 1.4.4 Sequence divergence is the basis for the evolutionary clock
Rapid lysis: Rapid lysis (r) mutants display a change in the pattern of lysis of E. coli at the end of an infection by a T-even phage.
Defined as key term in
Molecular Biology 7.32.3 Linkage and mapping
Reading frame: A reading frame is one of the three possible ways of reading a nucleotide sequence. Each reading frame divides the sequence into a series of successive triplets. There are three possible reading frames in any sequence, depending on the starting point. If the first frame starts at position 1, the second frame starts at position 2, and the third frame starts at position 3.
Defined as key term in
Molecular Biology—Essentials 1.2.10 Every sequence has three possible reading frames
Molecular Biology 1.1.22 Every sequence has three possible reading frames
Readthrough: Readthrough at transcription or translation occurs when RNA polymerase or the ribosome, respectively, ignores a termination signal because of a mutation of the template or the behavior of an accessory factor.
Defined as key term in
Molecular Biology—Essentials 2.9.11 Suppressor tRNAs have mutated anticodons that read new codons
Molecular Biology—Essentials 3.11.13 There are two types of terminators in E. coli
Molecular Biology 2.7.14 Suppressors may compete with wild-type reading of the code
Molecular Biology 3.9.20 Bacterial RNA polymerase terminates at discrete sites
Receptor: A receptor is a transmembrane protein, located in the plasma membrane, that binds a ligand in a domain on the extracellular side, and as a result has a change in activity of the cytoplasmic domain. (The same term is sometimes used also for the steroid receptors, which are transcription factors that are activated by binding ligands that are steroids or other small molecules.)
Defined as key term in
Cell Biology 1.1.20 Signal transduction pathways execute predefined responses
Molecular Biology 6.28.1 Introduction
Molecular Biology 6.28.5 G proteins may activate or inhibit target proteins
Receptor-mediated endocytosis [simple definition]: Receptor-mediated endocytosis is a type of endocytosis in which a specific type of molecule is taken into the cell after binding to cell surface receptors.
Defined as key term in
Introduction to Biology 3.12.10 Through endocytosis, cells recycle their surface membrane and ingest materials
Cell Biology 2.4.3 Overview of the endocytic pathway
Receptor-mediated endocytosis [advanced definition]: Receptor-mediated endocytosis is the process whereby soluble macromolecules are taken up after binding to cell surface receptors.
Defined as key term in
Introduction to Biology 3.12.10 Through endocytosis, cells recycle their surface membrane and ingest materials
Cell Biology 2.4.3 Overview of the endocytic pathway
Recessive: A recessive allele is obscured in the phenotype of a heterozygote by the dominant allele, often due to inactivity or absence of the product of the recessive allele.
Defined as key term in
Genetics 1.1.3 Traits can be dominant or recessive
Genetics 1.4.3 The impact of mutations on phenotypes
Genetics 2.7.13 An example of a genetic screen in yeast
Molecular Biology 7.32.2 Mendel's laws and dominance
Recessive-lethal: A recessive-lethal mutation is lethal as a homozygote but viable as a heterozygote with the corresponding wild-type allele.
Defined as key term in
Genetics 1.4.3 The impact of mutations on phenotypes
Reciprocal cross: A reciprocal cross means that relationships of the genes under study are reversed with regards to sex. If an original cross is female A × male B, the reciprocal cross is female B × male A, where A and B are the two genotypes.
Defined as key term in
Genetics 1.1.2 Mendel studied the garden pea
Reciprocal translocation: A reciprocal translocation exchanges part of one chromosome with part of another chromosome.
Defined as key term in
Molecular Biology 6.30.12 Proto-oncogenes can be activated by translocation
Recoding: Recoding events occur when the meaning of a codon or series of codons is changed from that predicted by the genetic code. It may involve altered interactions between aminoacyl-tRNA and mRNA that are influenced by the ribosome.
Defined as key term in
Molecular Biology—Essentials 2.9.12 Recoding changes codon meanings
Molecular Biology 2.7.16 Recoding changes codon meanings
Recognition helix: The recognition helix is the one of the two helices of the helix-turn-helix motif that makes contacts with DNA that are specific for particular bases. This determines the specificity of the DNA sequence that is bound.
Defined as key term in
Molecular Biology—Essentials 3.14.10 Repressor uses a helix-turn-helix motif to bind DNA
Molecular Biology 3.12.13 The recognition helix determines specificity for DNA
Recombinant: Recombinant progeny have a different genotype from that of either parent.
Defined as key term in
Molecular Biology 7.32.2 Mendel's laws and dominance
Recombinant congenic strain: A recombinant congenic strain is an inbred strain started from a cross between two different inbred strains followed by inbreeding from the N3 or N4 generation for at least 20 generations.
Defined as key term in
Genetics 2.11.14 Recombinant congenic and consomic strain sets are specialized genetic mapping tools
Recombinant DNA: Recombinant DNA is DNA that has been cut and spliced together in vitro to obtain the desired combination of DNA sequences.
Defined as key term in
Genetics 2.6.15 Recombinant DNA techniques use plasmids and phage to carry foreign pieces of DNA
Recombinant genotype: A recombinant genotype is one that consists of a new combination of genes produced by crossing over.
Defined as key term in
Molecular Biology 7.32.3 Linkage and mapping
Recombinant inbred: A recombinant inbred is an inbred strain started from a cross between two different inbred strains followed by inbreeding from the F2 generation for at least 20 generations.
Defined as key term in
Genetics 2.10.12 Genetic mapping uses recombination frequency to locate genes
Genetics 2.11.13 Recombinant inbred strain sets are specialized genetic mapping tools
Recombinant joint: A recombinant joint is the point at which two recombining molecules of duplex DNA are connected (the edge of the heteroduplex region).
Defined as key term in
Molecular Biology—Essentials 4.19.2 Breakage and reunion involves heteroduplex DNA
Molecular Biology 4.15.3 Breakage and reunion involves heteroduplex DNA
Recombination: Recombination describes the reciprocal or non-reciprocal transfer of heredity material between chromosomes.
Defined as key term in
Genetics 1.3.2 Physical recombination can occur between genes on homologous chromosomes
Genetics 1.3.3 Frequency of recombination is a measure of distance between genes
Recombination nodule: Recombination nodules are dense objects present on the synaptonemal complex; they may represent protein complexes involved in crossing-over.
Defined as key term in
Molecular Biology 4.15.5 Recombining chromosomes are connected by the synaptonemal complex
Recombination repair: Recombination repair is a mechanism for accurately bypassing a DNA lesion by using sequence information from the other parental strand or a different chromosome, sometimes by filling a gap in one strand of duplex DNA by retrieving a fragment of homologous single strand from another duplex.
Defined as key term in
Genetics 1.4.17 Avoiding mutagenesis — Overcoming replication blocks
Recombination-repair: Recombination-repair is a mode of filling a gap in one strand of duplex DNA by retrieving a homologous single strand from another duplex.
Defined as key term in
Molecular Biology—Essentials 4.20.7 Recombination-repair systems in E. coli
Molecular Biology 4.15.20 Repair systems correct damage to DNA
Rectification: Rectification is the property of ion channels in which the ion conductance changes in response to a change in membrane voltage.
Defined as key term in
Cell Biology 2.2.6 Different K⁺ channels use a similar gate coupled to different activating or inactivating mechanisms
Recycling endosome: Recycling endosomes serve as storage depots for endocytosed receptors and are the site of polarized membrane sorting in the endosomal system.
Defined as key term in
Cell Biology 2.4.15 Some receptors recycle from early endosomes whereas others are degraded in lysosomes
Reduction division: A reduction division reduces the number of chromosomes to half that of the original cell. This is accomplished by the first meiotic division.
Defined as key term in
Genetics 1.2.4 Reductional division occurs in meiosis
Reductionist: A reductionist approach to understanding a biological process consists of analyzing the underlying components.
Defined as key term in
Introduction to Biology 1.1.5 New properties emerge from the formation of complex systems
Redundancy: Redundancy describes the concept that two or more genes may fulfill the same function, so that no single one of them is essential.
Defined as key term in
Genetics 1.5.4 Isolating loss-of-function mutations in haploid organisms
Genetics 2.10.17 Suppressor and enhancer studies identify additional genes involved in a process
Genetics 2.8.16 Pleiotropy and redundancy are the two major obstacles in studying gene functions with simple null mutations
Genetics 2.9.16 Screens for genes with specific expression patterns eliminate the dependence on a mutant phenotype
Molecular Biology—Essentials 1.5.9 How many genes are essential?
Molecular Biology 1.3.15 How many genes are essential?
Regulated secretion: Regulated secretion is the triggered release from the cell of cargo molecules stored in secretory granules.
Defined as key term in
Cell Biology 2.4.19 Some cells store proteins for later secretion
Cell Biology 2.4.2 Overview of the exocytic pathway
Regulator gene: A regulator gene codes for a product (typically protein) that controls the expression of other genes (usually at the level of transcription).
Defined as key term in
Molecular Biology—Essentials 3.12.1 Introduction
Molecular Biology 3.10.1 Introduction
Relaxase: A relaxase is an enzyme that cuts one strand of DNA, and binds to the free 5′ end.
Defined as key term in
Molecular Biology—Essentials 4.16.5 Rolling circles are used to replicate phage genomes
Molecular Biology 4.13.11 Rolling circles are used to replicate phage genomes
Relaxed: Relaxed mutants of E. coli do not display the stringent response to starvation for amino acids (or other nutritional deprivation).
Defined as key term in
Molecular Biology—Essentials 2.8.12 Uncharged tRNA causes the ribosome to trigger the stringent response
Molecular Biology 3.11.8 (p)ppGpp is produced by the ribosome
Release factor: A release factor is required to terminate protein synthesis to cause release of the completed polypeptide chain and the ribosome from mRNA. Individual factors are numbered. Eukaryotic factors are called eRF.
Defined as key term in
Molecular Biology—Essentials 2.8.13 Three codons terminate protein synthesis and are recognized by protein factors
Molecular Biology 2.6.15 Termination codons are recognized by protein factors
releaser: A releaser is a sign stimulus displayed by another member of the same species.
Defined as key term in
Introduction to Biology 2.7.2 Ethologists study animals in their natural environment
Renaturation: Renaturation describes the reassociation of denatured complementary single strands of a DNA double helix.
Defined as key term in
Molecular Biology—Essentials 1.1.12 Nucleic acids hybridize by base pairing
Molecular Biology 1.1.9 Nucleic acids hybridize by base pairing
Repair: Repair of damaged DNA can take place by repair synthesis, when a strand that has been damaged is excised and replaced by the synthesis of a new stretch. It can also take place by recombination reactions, when the duplex region containing the damaged strand is replaced by an undamaged region from another copy of the genome.
Defined as key term in
Cell Biology 1.1.11 Cells require mechanisms to repair damage to DNA
Molecular Biology—Essentials 4.18.2 DNA polymerases are the enzymes that make DNA
Molecular Biology 4.14.2 DNA polymerases are the enzymes that make DNA
Repetition frequency: The repetition frequency is the (integral) number of copies of a given sequence present in the haploid genome; equals 1 for nonrepetitive DNA, >2 for repetitive DNA.
Defined as key term in
Molecular Biology 7.32.1 DNA reassociation kinetics
Repetitive DNA: Repetitive DNA behaves in a reassociation reaction as though many (related or identical) sequences are present in a component, allowing any pair of complementary sequences to reassociate.
Defined as key term in
Molecular Biology 1.3.6 Eukaryotic genomes contain both nonrepetitive and repetitive DNA sequences
Molecular Biology 7.32.1 DNA reassociation kinetics
Replacement site: Replacement sites in a gene are those at which mutations alter the amino acid that is coded.
Defined as key term in
Molecular Biology—Essentials 1.6.4 Sequence divergence is the basis for the evolutionary clock
Molecular Biology 1.4.4 Sequence divergence is the basis for the evolutionary clock
Replica plate: To replica plate is to precisely transfer a portion of each colony from one petri plate to another. This method enables the comparison of genetically identical cells under different conditions.
Defined as key term in
Genetics 1.5.4 Isolating loss-of-function mutations in haploid organisms
Genetics 2.6.11 Genetic screens allow detection of mutant bacteria, even though both mutant and wild-type bacteria can grow
Replicate: To replicate is to copy or duplicate.
Defined as key term in
Introduction to Biology 3.10.13 The two common types of nucleic acids in cells are DNA and RNA
Replication: Replication of duplex DNA takes place by synthesis of two new strands that are complementary to the parental strands. The parental duplex is replaced by two identical daughter duplexes, each of which has one parental strand and one newly synthesized strand. Replication is called semiconservative because the conserved units are the single strands of the parental duplex.
Defined as key term in
Molecular Biology—Essentials 4.18.2 DNA polymerases are the enzymes that make DNA
Molecular Biology 4.14.2 DNA polymerases are the enzymes that make DNA
Replication eye: A replication eye is a region in which DNA has been replicated within a longer, unreplicated region.
Defined as key term in
Molecular Biology—Essentials 4.15.2 An origin usually initiates bidirectional replication
Molecular Biology 4.13.2 Replicons can be linear or circular
Replication fork: A replication fork is the point at which strands of parental duplex DNA are separated so that replication can proceed. A complex of proteins including DNA polymerase is found at the fork.
Defined as key term in
Molecular Biology—Essentials 1.1.10 DNA strands separate at the replication fork
Molecular Biology—Essentials 4.15.2 An origin usually initiates bidirectional replication
Molecular Biology 1.1.8 DNA strands separate at the replication fork
Molecular Biology 4.13.2 Replicons can be linear or circular
Replication repair: In replication repair, the blocked strand switches to a different template, the daughter strand of the other parental strand, and later switches back to its cognate template. This is a template-switching or copy-choice mechanism.
Defined as key term in
Genetics 1.4.17 Avoiding mutagenesis — Overcoming replication blocks
Replication-defective: A replication-defective virus cannot perpetuate an infective cycle because some of the necessary genes are absent (replaced by host DNA in a transducing virus) or mutated.
Defined as key term in
Molecular Biology—Essentials 4.22.6 Retroviruses may transduce cellular sequences
Molecular Biology 4.17.6 Retroviruses may transduce cellular sequences
Replicative transposition: Replicative transposition describes the movement of a transposon by a mechanism in which first it is replicated, and then one copy is transferred to a new site.
Defined as key term in
Molecular Biology—Essentials 4.21.4 Transposition occurs by both replicative and nonreplicative mechanisms
Molecular Biology 4.16.4 Transposition occurs by both replicative and nonreplicative mechanisms
Replicon: The replicon is a unit of the genome in which DNA is replicated. Each replicon contains an origin for initiation of replication.
Defined as key term in
Molecular Biology—Essentials 4.15.1 Introduction
Molecular Biology 4.13.1 Introduction
Replisome: The replisome is the multiprotein structure that assembles at the bacterial replication fork to undertake synthesis of DNA. It contains DNA polymerase and other enzymes.
Defined as key term in
Molecular Biology—Essentials 4.18.1 Introduction
Molecular Biology 4.14.1 Introduction
Repolarization: Membrane repolarization is the phase of an action potential when the membrane potential returns to its resting value.
Defined as key term in
Cell Biology 2.2.12 Action potentials are electrical signals that depend on several types of ion channels
Cell Biology 2.2.4 Electrochemical gradients across the cell membrane generate the membrane potential
Reporter gene: A reporter gene is a coding unit whose product is easily assayed (such as chloramphenicol transacetylase or beta-galactosidase); it may be connected to any promoter of interest so that expression of the gene can be used to assay promoter function.
Defined as key term in
Genetics 2.10.6 Agrobacterium T-DNA can be used for insertional mutagenesis in Arabidopsis
Genetics 2.6.9 Mutations may be easily detected in bacteria
Molecular Biology—Essentials 6.32.3 Cloning vectors can be specialized for different purposes
Repressible: A repressible operon is expressed unless the small molecule co-repressor is present.
Defined as key term in
Molecular Biology 3.11.2 Distinguishing positive and negative control
Repression: Repression describes the ability of bacteria to prevent synthesis of certain enzymes when their products are present; more generally, refers to inhibition of transcription (or translation) by binding of repressor protein to a specific site on DNA (or mRNA).
Defined as key term in
Molecular Biology—Essentials 3.12.4 The lac operon can be induced
Molecular Biology 3.10.5 The lac operon can be induced
Repressor: A repressor is a protein that inhibits expression of a gene. It may act to prevent transcription by binding to an operator site in DNA, or to prevent translation by binding to RNA.
Defined as key term in
Introduction to Biology 3.12.4 The nucleus contains most of the genetic information
Genetics 2.6.16 Recombinant DNA techniques can be used to construct reporters that are useful for studying gene regulation
Molecular Biology—Essentials 3.12.1 Introduction
Molecular Biology 3.10.2 Regulation can be negative or positive
Rescue: In genetics, to rescue a mutant means to restore the wild-type phenotype.
Defined as key term in
Genetics 1.5.9 Building a genetic network requires additional screens
Cell Biology 4.7.5 Microtubule assembly and disassembly proceed by a unique process termed dynamic instability
Resolution: Resolution occurs by a homologous recombination reaction between the two copies of the transposon in a cointegrate. The reaction generates the donor and target replicons, each with a copy of the transposon.
Defined as key term in
Molecular Biology—Essentials 4.21.7 Replicative transposition proceeds through a cointegrate
Molecular Biology 4.15.3 Breakage and reunion involves heteroduplex DNA
Molecular Biology 4.16.7 Replicative transposition proceeds through a cointegrate
Resolvase: Resolvase is the enzyme activity involved in site-specific recombination between two copies of a transposon that has been duplicated.
Defined as key term in
Molecular Biology—Essentials 4.21.4 Transposition occurs by both replicative and nonreplicative mechanisms
Molecular Biology—Essentials 4.21.7 Replicative transposition proceeds through a cointegrate
Molecular Biology 4.16.4 Transposition occurs by both replicative and nonreplicative mechanisms
Molecular Biology 4.16.7 Replicative transposition proceeds through a cointegrate
Response element: A response element is a sequence in a eukaryotic promoter or enhancer that is recognized by a specific transcription factor.
Defined as key term in
Molecular Biology—Essentials 5.25.2 There are several types of transcription factors
Molecular Biology—Essentials 5.25.5 Response elements are recognized by activators
Molecular Biology 5.22.2 There are several types of transcription factors
Molecular Biology 5.22.7 Response elements are recognized by activators
Restriction endonuclease: Restriction endonucleases recognize specific short sequences of DNA and cleave the duplex (sometimes at target site, sometimes elsewhere, depending on type).
Defined as key term in
Molecular Biology—Essentials 1.3.2 Interrupted genes were first detected by comparing mRNA and DNA
Molecular Biology 1.2.3 Restriction endonucleases are a key tool in mapping DNA
Restriction fragment length polymorphism: Restriction fragment length polymorphism refers to inherited differences in sites for restriction enzymes (for example, caused by base changes in the target site) that result in differences in the lengths of the fragments produced by cleavage with the relevant restriction enzyme. RFLPs are used for genetic mapping to link the genome directly to a conventional genetic marker.
Defined as key term in
Genetics 2.11.15 Recombinant DNA and genomics techniques revolutionized mouse genetics
Genetics 2.8.11 Mapping mutations in C. elegans
Molecular Biology—Essentials 1.4.3 Individual genomes show extensive variation
Molecular Biology 1.3.3 Individual genomes show extensive variation
Restriction map: A restriction map is a linear array of sites on DNA cleaved by various restriction enzymes.
Defined as key term in
Molecular Biology—Essentials 1.3.2 Interrupted genes were first detected by comparing mRNA and DNA
Molecular Biology 1.2.3 Restriction endonucleases are a key tool in mapping DNA
Restrictive condition: A restrictive condition is an environmental condition under which a conditional mutant shows the mutant phenotype.
Defined as key term in
Genetics 1.5.4 Isolating loss-of-function mutations in haploid organisms
Retention signal: A retention signal is the part (or parts) of a protein that locates it in the correct membrane and prevents it from leaving the compartment. An example is the transmembrane domain of Golgi resident proteins.
Defined as key term in
Cell Biology 2.4.10 Retention of proteins in the Golgi apparatus depends on the membrane-spanning domain
Molecular Biology 6.27.11 Protein localization depends on specific signals
Retrieval signal: A retrieval signal is a type of sorting signal. It is the part (or parts) of a protein that mediates its return to the compartment in which it normally functions, should it inadvertently be transported to another compartment.
Defined as key term in
Cell Biology 2.4.7 Resident proteins that escape from the ER are retrieved
Retroelement: A retroelement (a retrotransposon or a retrovirus) alternates between DNA inserted into and replicating as part of a host chromosome and transcribed RNA either within the cell or in a virus particle.
Defined as key term in
Genetics 1.4.23 Measuring mutation rates in RNA genomes and in multicellular eukaryotes
Retrograde translocation: Retrograde translocation is the translocation of a protein from the lumen of the ER to the cytoplasm. It usually occurs to allow misfolded or damaged proteins to be degraded by the proteasome.
Defined as key term in
Cell Biology 2.3.19 Terminally misfolded proteins in the ER are returned to the cytoplasm for degradation
Cell Biology 2.3.2 Proteins enter the secretory pathway by translocation across the ER membrane (an overview)
Molecular Biology 2.8.13 Reverse translocation sends proteins to the cytosol for degradation
Retrograde transport: Retrograde transport is the movement of material from the Golgi apparatus (or from the plasma membrane) to the endoplasmic reticulum.
Defined as key term in
Cell Biology 2.4.8 COPI-coated vesicles mediate retrograde transport from the Golgi apparatus to the ER
Molecular Biology 6.27.4 Coated vesicles transport both exported and imported proteins
Retroposon: A retroposon is a transposon that mobilizes via an RNA form; the DNA element is transcribed into RNA, and then reverse-transcribed into DNA, which is inserted at a new site in the genome. The difference from retroviruses is that the retroposon does not have an infective (viral) form.
Defined as key term in
Genetics 1.4.23 Measuring mutation rates in RNA genomes and in multicellular eukaryotes
Molecular Biology—Essentials 4.22.1 Introduction
Molecular Biology—Essentials 4.22.7 Yeast Ty elements resemble retroviruses
Molecular Biology 4.17.1 Introduction
Molecular Biology 4.17.7 Yeast Ty elements resemble retroviruses
Retrotranslocation: Retrotranslocation (sometimes called dislocation) is the movement of proteins back across the membrane of the ER so that they can be degraded in the cyotplasm.
Defined as key term in
Biochemistry 1.4.7 Retrotranslocation from the endoplasmic reticulum back into the cytoplasm allows degradation of short-lived ER proteins
Retrovirus: A retrovirus is an RNA virus with the ability to convert its sequence into DNA by reverse transcription.
Defined as key term in
Genetics 1.4.23 Measuring mutation rates in RNA genomes and in multicellular eukaryotes
Immunology 5.12.1 Introduction
Molecular Biology—Essentials 4.22.1 Introduction
Molecular Biology 1.1.26 Genetic information can be provided by DNA or RNA
Molecular Biology 4.17.1 Introduction
Reverse genetics: Reverse genetics is a type of genetic analysis that begins with a known protein or gene. The goal is to mutate the gene (and thus the protein it encodes) to determine the mutant phenotype.
Defined as key term in
Genetics 2.6.7 Mutagenesis can be used to increase the frequency of a desired mutation to a detectable level
Genetics 2.8.14 C. elegans is a popular organism for reverse genetics
Reverse transcriptase: Reverse transcriptase is an enzyme that uses a template of single-stranded RNA to generate a double-stranded DNA copy.
Defined as key term in
Molecular Biology—Essentials 1.1.8 The structure of DNA allows replication and transcription
Molecular Biology—Essentials 4.22.2 The retrovirus life cycle involves transposition-like events
Molecular Biology—Essentials 4.22.4 Viral DNA is generated by reverse transcription
Molecular Biology 4.17.2 The retrovirus life cycle involves transposition-like events
Reverse transcription: Reverse transcription is synthesis of DNA on a template of RNA. It is accomplished by the enzyme reverse transcriptase.
Defined as key term in
Genetics 1.4.8 Studying mutation in somatic cells
Molecular Biology 1.1.26 Genetic information can be provided by DNA or RNA
Revertant: Revertants are derived by reversion of a mutant cell or organism to the wild-type phenotype.
Defined as key term in
Genetics 1.5.9 Building a genetic network requires additional screens
Genetics 2.10.7 Transposons can be used for insertional mutagenesis in Arabidopsis
Genetics 2.6.10 A genetic selection allows only the mutant class of organisms to grow
Molecular Biology—Essentials 1.1.15 The effects of mutations can be reversed
Molecular Biology 1.1.12 The effects of mutations can be reversed
RF1: RF1 is the bacterial release factor that recognizes UAA and UAG as signals to terminate protein synthesis.
Defined as key term in
Molecular Biology—Essentials 2.8.13 Three codons terminate protein synthesis and are recognized by protein factors
Molecular Biology 2.6.15 Termination codons are recognized by protein factors
RF2: RF2 is the bacterial release factor that recognizes UAA and UGA as signals to terminate protein synthesis.
Defined as key term in
Molecular Biology—Essentials 2.8.13 Three codons terminate protein synthesis and are recognized by protein factors
Molecular Biology 2.6.15 Termination codons are recognized by protein factors
RF3: RF3 is a protein synthesis termination factor related to the elongation factor EF-G. It functions to release the factors RF1 or RF2 from the ribosome when they act to terminate protein synthesis.
Defined as key term in
Molecular Biology—Essentials 2.8.13 Three codons terminate protein synthesis and are recognized by protein factors
Molecular Biology 2.6.15 Termination codons are recognized by protein factors
Rho factor: Rho factor is a protein involved in assisting E. coli RNA polymerase to terminate transcription at certain terminators (called rho-dependent terminators).
Defined as key term in
Molecular Biology—Essentials 3.11.13 There are two types of terminators in E. coli
Molecular Biology 3.9.21 There are two types of terminators in E. coli
Rho-dependent: Rho-dependent terminators are sequences that terminate transcription by bacterial RNA polymerase in the presence of the rho factor.
Defined as key term in
Molecular Biology—Essentials 3.11.13 There are two types of terminators in E. coli
Molecular Biology 3.9.21 There are two types of terminators in E. coli
Ri plasmid: Ri plasmids are found in Agrobacterium tumefaciens. Like Ti plasmids, they carry genes that cause disease in infected plants. The disease may take the form of either hairy root disease or crown gall disease.
Defined as key term in
Molecular Biology 4.18.13 The bacterial Ti plasmid causes crown gall disease in plants
Ribonuclease: Ribonucleases are enzymes that cleave RNA. They may be specific for single-stranded or for double-stranded RNA, and may be either endonucleases or exonucleases.
Defined as key term in
Molecular Biology—Essentials 1.1.10 DNA strands separate at the replication fork
Molecular Biology 1.1.8 DNA strands separate at the replication fork
Ribonucleic acid: Ribonucleic acid is a single-stranded nucleic acid that contains the sugar ribose and the base uracil. It plays a significant role in protein synthesis, but also constitutes the genome of some viruses.
Defined as key term in
Introduction to Biology 3.10.13 The two common types of nucleic acids in cells are DNA and RNA
Ribonucleoprotein: A ribonucleoprotein is a complex of RNA with proteins.
Defined as key term in
Molecular Biology 2.5.5 Messenger RNA is translated by ribosomes
Ribose: Ribose is the sugar component of RNA.
Defined as key term in
Introduction to Biology 3.10.13 The two common types of nucleic acids in cells are DNA and RNA
Ribosomal DNA: Ribosomal DNA is usually a tandemly repeated series of genes coding for a precursor to the two large rRNAs.
Defined as key term in
Molecular Biology—Essentials 1.6.7 Genes for rRNA form tandem repeats including an invariant transcription unit
Molecular Biology 1.4.8 Genes for rRNA form tandem repeats
Ribosomal RNA: Ribosomal RNA is a major component of the ribosome. Each of the two subunits of the ribosome has a major rRNA as well as many proteins.
Defined as key term in
Molecular Biology—Essentials 2.7.1 Introduction
Molecular Biology 2.5.1 Introduction
Ribosome: The ribosome is a large assembly of RNA and proteins that synthesizes proteins under direction from an mRNA template. Bacterial ribosomes sediment at 70S, eukaryotic ribosomes at 80S. A ribosome can be dissociated into two subunits.
Defined as key term in
Introduction to Biology 3.11.3 Cytoplasm contains structures vital to bacterial function
Molecular Biology—Essentials 2.7.5 Messenger RNA is translated by ribosomes
Molecular Biology 2.5.5 Messenger RNA is translated by ribosomes
Molecular Biology 7.32.6 ER and Golgi
Ribosome stalling: Ribosome stalling describes the inhibition of movement that occurs when a ribosome reaches a codon for which there is no corresponding charged aminoacyl-tRNA.
Defined as key term in
Molecular Biology—Essentials 3.13.5 Attenuation can be controlled by translation
Molecular Biology 3.11.17 Attenuation can be controlled by translation
Ribosome-binding site: A ribosome-binding site is a sequence on bacterial mRNA that includes an initiation codon that is bound by a 30S subunit in the initiation phase of protein synthesis.
Defined as key term in
Molecular Biology—Essentials 2.8.4 Initiation in bacteria needs 30S subunits and accessory factors
Molecular Biology—Essentials 2.8.6 mRNA binds a 30S subunit to create the binding site for a complex of IF-2 and fMet-tRNA_f
Molecular Biology 2.6.4 Initiation in bacteria needs 30S subunits and accessory factors
Riboswitch: A riboswitch is a catalytic RNA whose activity responds to a small ligand.
Defined as key term in
Molecular Biology—Essentials 3.13.7 Small RNA molecules can regulate translation
Molecular Biology—Essentials 5.27.4 Ribozymes have various catalytic activities
Molecular Biology 3.11.19 Small RNA molecules can regulate translation
Molecular Biology 5.25.4 Ribozymes have various catalytic activities
Ribozyme: A ribozyme is an RNA that has catalytic activity.
Defined as key term in
Molecular Biology—Essentials 5.27.1 Introduction
Molecular Biology 5.25.1 Introduction
Right-handed: A helix is said to be right-handed if the turns runs clockwise along the helical axis.
Defined as key term in
Molecular Biology—Essentials 1.1.6 DNA is a double helix
Molecular Biology 1.1.6 DNA is a double helix
RNA editing: RNA editing describes a change of sequence at the level of RNA following transcription.
Defined as key term in
Molecular Biology—Essentials 5.27.1 Introduction
Molecular Biology—Essentials 5.27.9 RNA editing occurs at individual bases
Molecular Biology 5.25.1 Introduction
Molecular Biology 5.25.10 RNA editing occurs at individual bases
RNA interference: RNA interference describes the technique in which double-strand RNA is introduced into cells to eliminate or reduce the activity of a target gene. It is caused by using sequences complementary to the double-stranded RNA sequences to trigger degradation of the mRNA of the gene.
Defined as key term in
Genetics 1.5.11 Screening without changing the genotype: RNAi, high copy plasmids.
Genetics 2.8.7 RNA interference is a powerful way to eliminate or reduce gene activity in the worm without changing the genotype
Molecular Biology—Essentials 3.13.10 RNA interference is related to gene silencing
Molecular Biology 3.11.22 RNA interference is related to gene silencing
RNA ligase: An RNA ligase is an enzyme that functions in tRNA splicing to make a phosphodiester bond between the two exon sequences that are generated by cleavage of the intron.
Defined as key term in
Molecular Biology—Essentials 5.26.13 Yeast tRNA splicing involves cutting and rejoining
Molecular Biology 5.24.14 Yeast tRNA splicing involves cutting and rejoining
RNA polymerase: RNA polymerases are enzymes that synthesize RNA using a DNA template (formally described as DNA-dependent RNA polymerases).
Defined as key term in
Molecular Biology—Essentials 1.1.8 The structure of DNA allows replication and transcription
Molecular Biology—Essentials 3.11.1 Introduction
Molecular Biology 1.1.8 DNA strands separate at the replication fork
Molecular Biology 3.9.1 Introduction
RNA silencing: RNA silencing describes the ability of a dsRNA to suppress expression of the corresponding gene systemically in a plant.
Defined as key term in
Molecular Biology—Essentials 3.13.10 RNA interference is related to gene silencing
Molecular Biology 3.11.22 RNA interference is related to gene silencing
RNA splicing: RNA splicing is the process of excising introns from RNA and connecting the exons into a continuous mRNA.
Defined as key term in
Molecular Biology—Essentials 1.3.1 Introduction
Molecular Biology—Essentials 5.26.1 Introduction
Molecular Biology 1.1.24 Several processes are required to express the protein product of a gene
Molecular Biology 1.2.1 Introduction
Molecular Biology 5.24.1 Introduction
Rolling circle: The rolling circle is a mode of replication in which a replication fork proceeds around a circular template for an indefinite number of revolutions; the DNA strand newly synthesized in each revolution displaces the strand synthesized in the previous revolution, giving a tail containing a linear series of sequences complementary to the circular template strand.
Defined as key term in
Molecular Biology—Essentials 4.16.4 Rolling circles produce multimers of a replicon
Molecular Biology 4.13.10 Rolling circles produce multimers of a replicon
Root nodule: A root nodule is a structure on the roots of plants that houses nitrogen-fixing bacteria.
Defined as key term in
Introduction to Biology 2.5.10 The cycling of nitrogen is done largely by bacteria
Root-shoot axis: The root-shoot axis is the axis extending between the root and the shoot of a plant. Most plant growth is oriented along this axis.
Defined as key term in
Cell Biology 7.16.3 The meristem provides new growth modules in a repetitive manner
Rotational positioning: Rotational positioning describes the location of the histone octamer relative to turns of the double helix, which determines which face of DNA is exposed on the nucleosome surface.
Defined as key term in
Cell Biology 3.6.22 Do nucleosomes lie at specific positions?
Molecular Biology—Essentials 6.29.10 Do nucleosomes lie at specific positions?
Molecular Biology 5.20.11 Do nucleosomes lie at specific positions?
Rough endoplasmic reticulum: Rough endoplasmic reticulum refers to the region of the endoplasmic reticulum to which ribosomes are bound. It is the site of synthesis of membrane proteins and secretory proteins.
Defined as key term in
Introduction to Biology 3.12.6 The secretory pathway delivers new proteins and lipids to the cell surface
Cell Biology 2.3.24 The ER is morphologically and functionally subdivided
Molecular Biology 7.32.6 ER and Golgi
RTK: RTK is an abbreviation for "receptor tyrosine kinase". These kinases are membrane-bound proteins with large cytoplasmic and extracellular domains. Specific binding of a ligand, such as a growth factor, to the extracellular domain causes the cytoplasmic domain to phosphorylate other proteins on tyrosine residues.
Defined as key term in
Molecular Biology 6.28.7 Protein kinases are important players in signal transduction

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