148 Key Terms (124/84) -- Biology Part I

148 Key Terms - 7-methylguanosine cap - modification added to the 5′ end of pre-mRNAs to protect mRNA from degradation and assist translation - aminoacyl tRNA synthetase - enzyme that “charges” tRNA molecules by catalyzing a bond between the tRNA and a corresponding amino acid - anticodon - three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon - CAAT box - (GGCCAATCT) essential eukaryotic promoter sequence involved in binding transcription factors - central dogma - states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins - codon - three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation - colinear - in terms of RNA and protein, three “units” of RNA (nucleotides) specify one “unit” of protein (amino acid) in a consecutive fashion - consensus - DNA sequence that is used by many species to perform the same or similar functions - core enzyme - prokaryotic RNA polymerase consisting of α, α, β, and β‘ but missing σ; this complex performs elongation - degeneracy - (of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous - downstream - nucleotides following the initiation site in the direction of mRNA transcription; in general, sequences that are toward the 3′ end relative to a site on the mRNA - exon - sequence present in protein-coding mRNA after completion of pre-mRNA splicing - FACT - complex that “facilitates chromatin transcription” by disassembling nucleosomes ahead of a transcribing RNA polymerase II and reassembling them after the polymerase passes by - GC-rich box - (GGCG) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter - hairpin - structure of RNA when it folds back on itself and forms intramolecular hydrogen bonds between complementary nucleotides - holoenzyme - prokaryotic RNA polymerase consisting of α, α, β, β‘, and σ; this complex is responsible for transcription initiation - initiation site - nucleotide from which mRNA synthesis proceeds in the 5′ to 3′ direction; denoted with a “+1” - initiator tRNA - in prokaryotes, called [latex]tRNA \frac{Met}{f}[/latex] and in eukaryotes, called tRNAi; a tRNA that interacts with a start codon, binds directly to the ribosome P site, and links to a special methionine to begin a polypeptide chain - intron - non–protein-coding intervening sequences that are spliced from mRNA during processing - Kozak’s rules - determines the correct initiation AUG in a eukaryotic mRNA; the following consensus sequence must appear around the AUG: 5’-GCC(purine)CCAUGG-3’; the bolded bases are most important - nonsense codon - one of the three mRNA codons that specifies termination of translation - nontemplate strand - strand of DNA that is not used to transcribe mRNA; this strand