Glossary P-R Flashcards
paralogs
Multiple copies of the same gene within the genome of individual species.
The multiple different copies of arose through gene duplication events and mutations subsequent to speculation, often leading to alternate activities or even different roles within the cell or organism as a result.
paratope
That region within the antigen-binding site of immunoglobulin module responsible for recognition epitope of structure
PCR
polymerase chain reaction
An efficient, simple, and rapid technique involving sequential logarithmic amplification of a segment of DNA in a test tube
Penetrance
Refers to the proportion of individuals heterozygous for a given dominant allele, or homozygous for a given process of allele, that expresses the affected phenotype
peptide-binding groove
that region of a Class I or II MHC molecule that is responsible for binding processed antigen peptides for presentation
peptidyl transferase
An enzymatic activity of the ribosome responsible for formation of the peptide bond between the nascent polypeptide chain and the amino acid carried by the charged tRNA in the A site of the ribosome. In so doing, the ribosome is moved along the mRNA by one codon.
peptidyl-tRNA
the form of a tRNA molecular that is actively involved in polypeptide elongation, and has the nascent polypeptide chain attached
phage
A virus that infects a bacteria host, used in the laboratory as a cloning vector
phase variation
Alternation in the type of the flagellum produced by bacterium
Phenotype
The physical characteristics of a cellular organism that results from its unique genotype
phosphodiester bond
The two sequential mixed ester bonds formed between two ribose (RNA) or two 2-deoxyribose (DNA) molecules and the phosphate group between them, in the “backbone” of a nucleic acid
physical map
Analysis of the distance, between base pairs, between loci
planar molecule
A molecule that has an overall “flat” structure, such as benzene or its derivatives
plasmid
A class of circular extrachromosomal elements found in many bacteria. Contain origins of replication to ensure their maintenance.
Often modified for use in gene cloning or to alter the characteristics of the bacteria
Point mutation
a mutation in a single base pair within a DNA molecule
polarity
in this context, this term refers to the orientation of the sugar-phosphate backbone of a nucleic acid molecule. The 5’ end is terminated by a phosphate group, whereas the 3’ end is terminated with a hydroxyl group
polyacrylamide
a sieving matrix made by chemically cross-linking acrylamide, usually with bis-acrylamide, and free radical generators
Polyadenylation
The first to the addition of numerous non-templated “A” bases to the 3’ end of a nascent hnRNA transcript
Polycistronic
refers to a form of gene organization resulting in transcription of an mRNA that contains the coding sequences for multiple gene products, each of which is independently translated from the mRNA
polygenic disease
a disease that may be caused by mutations in any of several genes, but does not require mutation of more than one gene
polypeptide
The unique string of amino acids created by the translation of mRNA sequences.
This may require additional polypeptides subunits and/or functional groups in order to form a complete holoprotein
polyprotein
The giant polypeptide that contains multiple individual proteins sequences embedded within it and which is proteotypically cleaved to yield the individual proteins
polytene chromosome
Multiple, precisely aligned, identical copies of interphase chromosomes. Appear with light and dense alternating bands, characteristic of the chromosome and organism, based on localized states of condensation
primase
an DNA-dependent RNA polymerase function that synthesizes a short RNA primer used during DNA replication by DNA polymerase.
does not require a primer, only a template
prion
an infectious agents thought to be composed solely of protein
The prion protein is a normal protein, PrPc, that is expressed within neural tissues. In the abnormal prion state, the PrPc protein has undergone covalent modification and confirmational changes that render resistant to cellular degradation and autocatalytic, resulting in PrPsc (for scrapie form). PrPsc is thought to induce the re-folding of PrPc to make more of itself.
Processivity
refers to the degree and pace at which continuous synthesis of a nascent nucleic acid occurs
Promoter (site)
Region of a DNA molecule 5’ to a coding sequence that is responsible for assembly of an RNA polymerase complex and the initiation of transcription
proof-reading
Mechanism for correction of errors made during synthesis of nucleic acids or polypeptides by scrutiny of the products after the nucleotides or amino acids have already been incorporated
proteasome
A specialized organelle within the cytoplasm of the cell that is responsible for degradation of cytoplasmically situated proteins. The proteasome plays a key role in normal protein turnover and in peptide presentation by MHC Class I anigen
protein
refers to the complete, assembled form of a holoprotein, containing all necessary apoprotein subunits. For example, hemoglobin is comprised of two α and two β subunits, each of which contains a heme prosthetic group
proto-oncogene
Normal gene that may become an oncogene; also called cellular ocogene
purine
An orgnanic molecule the structure of which forms the basis in the nucleic acid bases adenine and guanine
pyrimidine
An orgnanic molecule the structure of which forms the basis in the nucleic acid bases cytosine, thymine, and uracil.
pyrimidine dimers
Covalent adducts formed between two pyrimidine basis, usually adjacent to one another in the same strand. Often involves formation of a cyclobutane ring structure.
Reading frame
The register in which a nucleic acid sequence is read, in 3-base increments, for translation into polypeptide.
May be either a real or virtual translation.
recessive
allele that determines phenotype only when homozygous; does not affect phenotype when heterozygous with a dominant allele
recombinant
Slang referring to an organism that carries a recombinant DNA molecule, often with some alteration in its phenotype
recombinant DNA
The combination of a foreign DNA insert with a vector DNA (e.g. plasmid, phage, cosmid, etc.) to produce a clone within a host organism
recombinase
enzymatic activity responsible for facilitating intra- or intermolecular recombination of DNA molecules
recombination
the rearrangement of DNA by breaking and re-ligations of the DNA strands
also called crossovers
replication
the act of a cell making a copy of all or some part of its genomic DNA
replicon
a segment of genomic DNA that contains an origin of replication and is replicated under the control of that origin
Repression
A form of gene regulation wherein the promoter is prevented from assembling and RNA polymerase, so that transcription does not occur
derepression refers to a loss of repression
restriction mapping
The creation of a physical map by ordering and enzymatilcally cut DNA fragments
restriction endonucleases
an enzyme, isolated from bacteria, that recognizes specific base-pair sequences within DNA and causes endonucleolytic cleavage of the DNA at a site determined by the recognized DNA sequences.
The sites vary from frequent to rare cutting, depending upon the length of the restriction site
Restriction fragment length polymorphism (RFLP)
Variation in the distance between restriction enzyme cleavage sites that exist within a population producing unique DNA fingerprint patterns
Reverse transcriptase
An enzyme that catalyzes the RNA dependent polymerization DNA.
This enzymatic activity is found in retroviruses.
RFLP
Restriction fragment length polymorphism
Variation in the distance between restriction enzyme cleavage sites that exist within a population producing unique DNA fingerprint patterns
ribosome
The large, multi-subunit ribonucleoprotein complex responsible for the translation of mRNA into polypeptide sequences
ribosome binding site
ribosome entry site
Sequences contained in an mRNA that organize the assembly of a ribosome to initiate translation of the mRNA into polypeptide
RNA
ribonucleic acid
single-strand nucleic acid found mainly int he nucleolus and ribosomes.
Contains ribose and uracil
RNAi
RNA interference
refers to the mechanism controlling transcript abundance through the induced degradation of transcripts by small (20-25 nt), complementary RNA fragments.
RNA polymerase
Enzymatic activity responsible for DNA dependent synthesis of RNA.
prokaryotes = 1 type of RNA Pol.
eukaryotes - 3 types of RNA Pol. each transcribes a different group of genes
rRNA
ribosomal RNA
RNAs which make up the scaffold upon which the ribosomal proteins are assembled to create the ribosomal subunits
RT-PCR
reverse-transcriptase-polymerase-chain-reaction
starts with RNA. Since RNA cannot be amplified by PCR it must first be reverse transcribed into cDNA in order to have an amplifiable target molecule.
May also be called real-time PCR and refers to time and cycle dependent PCR. (pay attention to context)
