R Arginine in proteins RACE Rapid Amplification of cDNA Ends. A PCR-based technique
for mapping the end of an RNA molecule radiation hybrid A hybrid cell produced by the fusion of a human cell and
a rodent cell, after they human cell has bee irradiated with
gamma rays to fragment the DNA radiation hybrid mapping The use of radiation hybrid cell panels to map genetic
markers, like STSs. radical substitution The substitution of an amino acid by another with
markedly different chemical properties radioactive marker A radioactive atom incorporated into a molecule and whose
radioactive emissions are subsequently used to detect and
follow that molecule during a biochemical reaction radiolabeling the technique for attaching a radioactive atom to a
molecule Ramachandran map A contour plot of the different phi and psi angles that
are found within a protein. The map shows that many
combinations of phi-psi angles are not found in proteins
(due to steric conflicts). random genetic drift The fluctuation in allele frequencies from generation to
generation caused by chance events, such as gamete
sampling. Ras A protein involved in signal transduction rate-limiting step rate of gene substitution The number of gene substitutions per locus per unit
time rate of mutation The number of mutations per locus or nucleotide site per
unit time, usually per generation time. rate of nucleotide substitution The number of nucleotide substitutions per nucleotide
site per unit time reading frame One of the three overlapping sequences of triplet codons
contained in a DNA sequence. readthrough mutation a mutation that changes a termination codon into a codon
specifying an amino acid, and hense results in readthrough
of the termination codon RecA An E. coli protein involved in homologous
recombination RecBCD enzyme An enzyme complex involved in homologous recombination in
E. coli. Recessive The allele that is not expressed in a heterozygote reciprocal strand exchange The exchange of DNA between two double-stranded
molecules, occurring as a result of recombination, such that
the end of one molecule is exchanged for the end of the
other molecule. Recognition helix An alpha helix in a DNA binding protein, one that is
responsible for recognition of the target nucleotide
sequence. recognition sequence The sequence recognized by a restriction endonuclease. In
many cases, a short palindrome. recombinant A progeny member that possesses neither of the
combinations of alleles displayed by the parents. Recombinant DNA molecule A DNA molecule created in the test-tube by ligating
pieces of DNA that are not normally joined together. Recombinant DNA technology the techniques involved in the construction, study and
use of recombinant DNA molecules. recombinant protein A protein synthesized in a recombinant cell due to
expression of a cloned gene recombinase A diverse family of enzymes that catalyze site-specific
recombination events. recombination A general term for several mechanisms resulting in the
breaking or cutting and resplicing of intervals of DNA.
Occurs both naturally and in the laboratory. recombination frequency The proportion of recombinant progeny arising from a
genetic cross recombination hotspot A region of a chromosome where crossovers occur at a
higher frequency than the average for the chromosome as a
whole recombination repair A DNA repair process that mends double-stranded
breaks. recursion The process of solving a large problem by reducing it to
one or more subproblems which are Once the original subdivision has been made, the same
decompositional technique is used to divide each of these
subproblems into new ones which are even less complex.
Eventually, the subproblems become so simple, that they can
be solved without further subdivision. referential integrity A database concept that asserts that a value appearing in
one context also appears in another, related context. That
is, if object A is related to object B, then B must really
exist. The database system must make sure that referential
integrity is not violated. regional duplication A duplication involving less than the entire genome regular expression A string of characters specifying a pattern. Usually,
wildcards (match to anything) and variable positions (match
to one of the following) are allowed. A consensus sequence
is a restricted form of a regular expression that allows
only one possibility at each position. regulatory gene A nontranscribed gene. Sometimes used to denote a
structural gene engaged in the regulation of gene
expression. regulatory mutant A mutant that has a defect in a promoter or other
regulatory sequence regulatory regions A DNA base sequence that controls gene expression relational database A type of database where the individual entries are
broken up and stored in "tables". With this type of
datasbase, it's possible to build sophisticated queries to
extract information from the database. relative rate test A calibration-free test for checking the constancy of the
rate of nucleotide substitutions in different lineages
during their evolution, thus determining whether or not the
moleculr clock operates at the same rate among different
lineages. release factor A protein that plays an ancillary role during termination
of translation renaturation The return of a denatured molecule to its natural
state. repetitive DNA A DNA sequence that is repeated two or more times in a
DNA molecule or genome repetitive DNA fingerprinting a clone fingerprinting technique that involves
determining the positioins of genome-wide repeats in cloned
DNA fragments repetitive DNA PCR A clone fingerprinting technique that uses PCR to detect
the relative positions of genome-wide repeats in cloned DNA
fragments. replacement The result of a nonsynonymous substitution at the protein
level Replica plating A technique for transfer of colonies from one Petri dish
to another, such that their relative positions on the
surface of the agar medium are retained. replication factory A large structure attached to the nuclear matrix; the
site of DNA replication replication fork The region of a double-stranded DNA molecule that is
being opened up to enable DNA replication to occur. replication protein A The main single-strand binding protein involved in
replication of eukaryotic DNA replication slippage A process in which a certain sequence of DNA is used more
than once in a row as a template during DNA replication,
thus creating a tandemly repeated sequence in the newly
synthesized DNA. This happens in microsatellite DNA. replicative transposition transposition that results in copying of the transposable
element. The insertion of a copy of a transposable element
into a new chromosomal position while the element itself
remains in the original position. replicator gene A regulatory gene specifying the sites for initiation and
termination of DNA replication. replicon A chromosomal region that contains the DNA sequences
necessary for the initiation of DNA replication, and that is
replicated as a unit. replisome A complex of proteins involved in DNA replication. reporter gene A gene whose phenotype can be assayed and which can
therefore be used to determine the function of a regulatory
DNA sequence. beta-galactosidase is a common reporter gene
because when expressed in the presence of XGAL, it will
convert XGAL into a blue dye that is visible in tissues or
gels. reproductive barrier Any of several biological or environmental mechanisms
that prevent gene exchange betweenpopulations residue A single unit in a polymer. Used for both a single
nucleotide in DNA or a single amino acid in a protein. resolution The degree of molecular detail on a physical map of DNA,
ranging from low to high. restriction endonuclease An enzyme that cuts DNA molecules at a limited number of
specific nucleotide sequences. restriction mapping Determination of the positions of restriction sites in a
DNA molecule by analyzing the sizes of restriction
fragments. restrictive conditions Conditions under which a contidional-lethal mutant is
unable to survive retroelement a genetic element that transposes via an RNA
intermediate retrofection Transfer of an RNA molecule from one cell to another, in
particular to a germ-line cell, by means of a retroviral
particle, into which the RNA is encapsulated. The RNA is
then reverse-transcribed and incorporated into the host
genome. retrogene A functional retrosequence producing a protein that is
identical or nearly identical to that produced by the gene
from which the mRNA was derived retron A genomic sequence encoding reverse transcriptase but
lacking the ability to transpose retropositon A RNA-mediated mode of transposition retroposon A transposable retroelement that neither constructs
virion particles nor is flanked by terminally redendant
sequences. retrosequence A genomic sequence that has been derived through tthe
reverse transcription of RNA but by itself lacks the ability
to produce reverse transcriptase. retrotransposon A genome-wide repeat with a sequence similar to an
integrated retrovirral genome and possibly with
retrotransposition activity. retroviral-like element A truncated retroviral genome integrated into a host
chromosome retrovirus A virus with an RNA genome that integrates into the
genome of its host cell reverse transcriptase A polymerase that synthesizes DNA on an RNA template RFLP Restriction Fragment Length Polymorphism -A restriction
fragment whose length is variable because of the presence of
a polymorphic restriction site at one or both ends.
Polymorphic sequeces taht result in RFLPs are used as
markers on both physical maps and genetic linkage maps.
RFLPs are usually caused by a mutation at a cutting
site. Rho helicase a protein requried for termination of some bacterial
transcripts ribbon-helix-ribbon motif A type of DNA-binding domain ribonuclease an enzyme that degrades RNA ribonuclease D An enzyme involved in processing pre-tRNA in bacteria ribonuclease P An enzyme involved in processing pre-tRNA in bacteria ribosomal protein One of the protein components of the ribosome ribosomal RNA (rRNA) the RNA molecules that are components of ribosomes ribosome A large complex made of RNA and protein where the protein
defined by a messenger RNA is synthesized ribosome binding site The nucleotide sequence that acts as the attachment site
for the small subunit of the ribosome during initiation or
translation in bacteria ribozyme An RNA molecule that has catalytic activity RNA Ribonucleic acid, one of the two forms of nucleic acid in
living cells; the genetic material for some viruses RNA dependent DNA polymerase An enzyme that makes a DNA copy of an RNA template; a
reverse transcriptase RNA editing A process by which nucleotides not coded by a gene are
introduced at specific positions in an RNA molecule after
transcription RNA polymerase An enzyme that synthesizes RNA on a DNA or RNA
template RNA polymerase I The eukaryotic RNA polymerase that transcribes ribosomal
RNA genes RNA polymerase II The eukaryotic RNA polymerase that transcribes
protein-coding and SNRNA genes RNA polymerase III The eukaryotic RNA polymerase that transcribes transfer
RNA nad other short genes. RNA transcript A RNA copy of a gene RNA world The early period of evolution when all biological
reactions were centered on RNA rolling circle replication A replication process that involves continual synthesis
of a polynucleotide which is "rolled-off" of a circular
template molecule. root In rooted trees, the common ancestor of all teh taxa
under study. rooted Refers to a phylogenetic tree tha tprovides information
on the past evolutionary events that have led to the
organisms or DNA sequences being studied. rooted tree A phylogenetic tree that specifies ancestral and
descendant species, thus indicating the direction of the
evolutionary path. root mean square deviation RMSD - A method in molecular modeling of measuring the
difference between different configurations of the same
molecule. rt-PCR Reverse Transcriptase PCR PCR in which the first step is
carried out by reverse transcriptase, so RNA can be used as
the starting material. Can be used to monitor levels of
expression.
