Glossary S-Z Flashcards
screening
Term given to act of assaying recombinants for a particular sequence of traits.
Can take many forms, depending upon the methodologies available.
semiconservative replication
term refering to the retention of one parental strand along with one nascent strand during DNA replication
Sequence homology
Similarities in nucleic acid sequence and organization, and in their encoded products, that are sufficiently great as to imply common ancestral origins
Sequence similarity
Similarity in nucleic acid or polypeptide sequences, particularly in shorter segments, that may not be sufficient to imply common ancestral origins
sex-linked
a trait transmitted by one of the chromosomes determining sex of an individual
short arm (p)
One of the two prominent segments of a chromosome
the long or “q” arm is the other
the arms of a given chromosome join at its centromere
Shuttle vector
A type of cloning vector that contains sequences enabling it to be propagated and maintained in more than one type of host (e.r. E. coli and mammalian cells)
single recognition particle (SRP)
a chaperonin complex responsible for arresting polypeptides synthesis and facilitating the docking of a ribosome to the endoplasmic reticulum membrane.
normally, on ribosomes translating polypeptides destined for insertion into or across the endoplasmic reticulum membrane become associated with SRP
siRNA
refers to “small interfering RNAs” that are formed from the nucleolytic processing of larger double stranded RNA regions into 21 nt molecules, one of which associates with the RISC complex and provides specificity to the cleavage of other related RNAs
snRNA
refers to the small nuclear RNAs that are or become part of spiceosomal complexes.
somatic
refers to non-germline cells
Somatic cells may become terminally differentiated with alterations in their overall genetic complement, because they are NOT responsible for passing along the organism’s genetic material to the offspring
Somatic hypermutation
A very high frequency of the mutational events that occur in specific loci, such as the variable segments of expressed immunoglobulin genes
in immunoglobulin genes this occurs after all rearrangements how occurred and provide additional potential for a variation in immunoglobulin structure
Southern blot
The transfer of size-separated DNA fragments to a synthetic membrane for further studies
initially described by E.N. Southern
Splice sequence
a sequence within an mRNA molecule that is the site at which splicing occurs
Spliceosome
A ribonucleoprotein structure responsible for splicing of primary transcripts
Sporadic
Not familial
Start codon
The codon at which translation of an mRNA molecule begins
in eukaryotes and most prokaryotes this is always AUG (encoding methionine)
in prokaryotes N-formyl-methionine is used to initiate polypeptide synthesis
stop codon
The codon at which translation of an mRNA molecule into a polypeptide is terminated
in the Universal Code this may be: UGA, UAG, or UAA
Stringency
A measure of the rigorousness of an attempt to separate two components
Often applied to nucleic acid hybridization conditions to indicate the likely degree of sequence homology between probe and target sequences
synteny
The conservation of gene groupings and organization on the chromosomes of different species of organisms
Telomerase
a ribonucleoprotein complex that maintains the repeat structures at the telomeric ends of chromosomes
telomere
The natural distal end of a chromosome
Contains some form of simple repeating sequence, usually with a Single stranded distal end that may form a hairpin
Template
an original form from which a copy is made using information present in the original
Termination sequence
The point in a DNA sequence at which transcription of a gene into RNA ceases
TFIID
transcription factor IID
Also know as “TATA factor”
Necessary for the assembly of RNA polymerase for transcription of essentially all eukaryotic mRNAs
thymine
one of the pyrimidine bases found in DNA
2,4-dihydroxy-5-methylpyrimidine
topoisomerase
An enzymatic activity responsible for relieving excessive supercoiling in DNA
Trans-
located on two physically dis-contiguous DNA molecules
transcribe
to copy DNA into RNA
transcription
the process wherein DNA is copies into RNA (often mRNA)
Transcription factor
A protein whose function is to control the act of transcription
Transcription start site
The point in a DNA sequence at which transcription of the gene into RNA begins
Transcriptional control
gene control exerted at the level of transcription
Transduction
The Incorporation of a cellular gene into a viral genome, that can then be introduced into other cells
Transfection
The process of placing foreign DNA into mammalian cells
also sometimes used to refer to insertion of foreign DNA into bacteria using bacteriophage
Transformation
The cancerous alteration of mammalian cells
also the act of putting foreign DNA into bacteria
Transformed phenotype
Acquisition of the phenotype characteristic of oncogenetic transformation
transgenic
an individual in which genetic modification has occurred in the germline tissues may be transmitted to subsequent generations
Transition mutation
A point mutation involving the substitution of a purine for a purine, or a pyrimidine for a pyrimidine
translation
The process of converting the nucleic acid language of the genetic code into the amino acid language of polypeptides, catalyzed by the ribosome and a host of soluble factors
mRNA codons are recognized by tRNA anti-codons. Each tRNA translates a single codon into a single amino acid, resulting in synthesis of polypeptide wherein the amino acid sequence is dictated by and matches the order of the codons in the mRNA
Translational control
Gene control exerted at the level of mRNA translation
Translational frame shifting
A mechanism used by certain viruses and even higher organisms to change the reading frame used during translation of an mRNA molecule, in a controlled manner, so that the polypeptide product is the result of translation in more than one reading frame
Transposable elements
Genetic elements characterized by their abilities to insert into withdraw from a given location within the genome, resulting in movement from site to site within the genome over a period of time
may cause epigentic changes in phenotype
transversion mutation
A point mutation involving the substitution of a purine for a pyrimidine, or vice versa
trinucleotide repeat
a highly reiterative sequence comprised entirely of a single trinucleotide sequence
Changes in the length of the repeat regions of many genes are associated with a number of genetic diseases
tRNA
transfer RNA
special RNAs that are charge with amino acids and which carry anticodons for recognition of the codons in mRNA
Responsible for translation from the language of nucleic acids into the language of polypeptides
each tRNA can be charged with only one type of amino acid, although multiple tRNAs exist for many of the amino acids
Tumor suppressor
A gene that prevents to tumor formation until deleted or mutated
turnover
The balance between synthesis and degradation of the product
The particular balance will affect the levels of accumulation of the product
umber mutation
one wherein a codon has been modified, resulting in the formation of a UGA stop codon
unifactorial
caused by mutations in a single, specific gene
universal genetic code
the “standard” codon usage that is common to most organisms
untranslated region
mRNA sequences that lie 5’ and 3’ to the sequences that are translated into polypeptide
uracil
one of the pyrimidine bases found in RNA
2,4-dihydroxypyrimidine
vector
a construct use to propagate DNA in a host (bacteria, yeast, or cultured cells)
virion
a replication-competent virus particle
Western analysis
Reaction of specific immunoglobulin(s) with proteinaceous antigens separated by electrophoretic mean and transferred to membranous support
used to identify those which carry epitopes recognized by the immunoglobulin(s)
usually the proteins are first separated by size, so that information is gained about the approximate mass of recognized polypeptide(s)
Yeast artificial chromosome (YAC)
a vector used in yeast that contains centromeric and telomeric sequences, and origins of replication so that is may be maintained and propagated
Used as cloning vectors which can propagate very large fragments of foreign DNA
