front 1 Gene expression | back 1 The process by which information encoded in DNA directs the synthesis of proteins, or, in some cases, RNAs that are not translated into proteins and instead function as RNAs |
front 2 Messenger RNA (mRNA) | back 2 A type of RNA synthesized using a DNA template that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein |
front 3 Transcription | back 3 The synthesis of RNA using a DNA template |
front 4 Translation | back 4 The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of the "language" from nucleotides to amino acids |
front 5 Primary transcript | back 5 An initial RNA transcript from any gene; also called pre-mRNA when transcribed from a protein-coding gene |
front 6 Triplet code | back 6 A genetic information system in which sets of three-nucleotide long words specify the amino acids for polypeptide chains |
front 7 Template Strand | back 7 The DNA strand that provides the pattern, or template, for ordering, by complementary base pairing, the sequence of nucleotides in an RNA transcript |
front 8 Codons | back 8 A 3-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code |
front 9 Reading frame | back 9 On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis |
front 10 RNA polymerase | back 10 An enzyme that links ribonucleotides into a growing RNA chain during transcription, based on complementary binding to nucleotides on a DNA template strand |
front 11 Promoter | back 11 A specific nucleotide sequence in the DNA of a gene that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place |
front 12 Terminator | back 12 In bacteria, a sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA |
front 13 Transcription unit | back 13 A region of DNA that is transcribed into an RNA molecule |
front 14 Start point | back 14 In transcription, the nucleotide position on the promoter where RNA polymerase begins synthesis of RNA |
front 15 Transcription factors | back 15 A regulatory protein that binds to DNA and effects transcription of specific genes |
front 16 Transcription initiation complex | back 16 The completed assembly of transcription factors and RNA polymerase bound to a promoter |
front 17 TATA Box | back 17 A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex |
front 18 RNA processing | back 18 Modification of RNA primary transcripts, including splicing out of introns, joining together of eons and alteration of the 5' and 3' ends |
front 19 5' cap | back 19 A modified form of guanine nucleotide added onto the 5' end of a pre-mRNA molecule |
front 20 poly-A tail | back 20 A sequence of 50-250 adenine nucleotides added onto the 3' end of a pre-mRNA molecule |
front 21 RNA splicing | back 21 After synthesis of a eukaryotic primary RNA transcript, the removal of portions of the transcript (introns) that will not be included in the mRNA and the joining together of the remaining portions (exons) |
front 22 Introns | back 22 A noncoding, intervening sequence within a primary transcript that is removed from the transcript during RNA processing; also refers to the region of DNA from which this sequence was transcribed |
front 23 Exons | back 23 A sequence within a primary transcript that remains in the RNA after RNA processing; also refers to the region of DNA from which this sequence was transcribed |
front 24 Spliceosome | back 24 A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons |
front 25 Ribozymes | back 25 An RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing |
front 26 Alternative RNA splicing | back 26 A type of eukaryotic gene regulation at the NRA-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 |
front 27 Domains | back 27 A discrete structural and functional region of a protein |
front 28 Transfer RNA (tRNA) | back 28 An RNA molecule that functions as a translator between nucleic acid and protein languages by carrying specific amino acids to the ribosome, where they recognize the appropriate codons in the mRNA |
front 29 Anticodon | back 29 A nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule |
front 30 Aminoacyl-tRNA synthetases | back 30 An enzyme that joins each amino acid to the appropriate tRNA |
front 31 Wobble | back 31 Flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon |
front 32 Ribosomal RNA (rRNA) | back 32 RNA molecules that, together with proteins, make up ribosomes, the most abundant type of RNA |
front 33 P site | back 33 Holds the tRNA carrying the growing polypeptide chain |
front 34 A site | back 34 Holds the tRNA carrying the next amino acid to be added to the polypeptide chain |
front 35 E site | back 35 The place where discharged tRNAs leave the ribosome (exit) |
front 36 Release Factor | back 36 A protein shaped like an aminoacyl tRNA, bunds directly to the stop codon in the A site |
front 37 Signal peptide | back 37 A sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide that targets it to the endoplasmic reticulum or other organelles in a eukaryotic cell |
front 38 Signal-recognition particle (SRP) | back 38 A protein-RNA complex that recognizes a signal peptide as it emerges from a ribosome and helps direct the ribosome to the ER by binding to a receptor protein on the ER |
front 39 Polyribosomes (Polysomes) | back 39 A group of several ribosomes attached to, and translating, the same messenger RNA moleucle |
front 40 Point mutations | back 40 A change in a single nucleotide pair of a gene |
front 41 Nucleotide-pair substitutions | back 41 A type of point mutation in which one nucleotide in a DNA strand and its partner in the complementary strand are replaced by another pair of nucleotides |
front 42 Silent Mutation | back 42 A nucleotide-pair substitution that has no observable effect on the phenotype |
front 43 Missense mutation | back 43 A nucleotide-pair substitution that results in a codon that codes for a different amino acid |
front 44 nonsense mutation | back 44 a mutation that changes a amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein |
front 45 insertions and deletions | back 45 a mutation involving the addition or loss of one or more nucleotide pairs to a gene |
front 46 frameshift mutation | back 46 a mutation occurring when nucleotides are inserted in or deleted from a gene and the number inserted or deleted is not multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons |
front 47 mutagens | back 47 a chemical or physical agent that interacts with DNA and can cause a mutation |