NAU BIO 181 Exam 2 Questions and Answers(A+ Solution guide)

Gene Expression - Process by which DNA directs protein synthesis; transcription and translation Transcription - Synthesis of RNA under DNA direction; Produces mRNA; use same language Translation - Synthesis of polypeptide under RNA direction; Nucleic acids and amino acids use different language, Ribosomes are site of translation Triplet code - Series of three-nucleotides (make amino acids) Template strand - Provides template for RNA transcription mRNA base triplets - Codons Direction codons are read during transcription - 5' to 3' direction RNA Polymerase - Pries DNA strand apart and hooks together RNA nucleotides Promoter - DNA sequence where RNA Polymerase attaches Transcription initiation complex - RNA Polymerase 2 bound to a promoter TATA Box - Crucial in forming initiation complex in eukaryotes 5' end of pre-mRNA molecule - Receives modified nucleotide 5' cap 3' end of pre-mRNA molecule - Gets poly-A tailRNA Splicing - Removes introns and joins exons, creating mRNA molecule with continuous coding sequence tRNA - Helps translate mRNA into protein aminoacyl-tRNA Synthetase - Matches correct tRNA and amino acid Where does translation occur? - Large subunit of ribosome P site - Holds tRNA that carries growing polypeptide chain A site - Holds tRNA that carries next amino acid to be added to chain E site - Exit site, where discharged tRNAs leave ribosome Elongation stage - Amino acids are added one by one to preceding amino acid Signal recognition particle - Signals synthesizing ribosome to move through rough ER When does termination occur? - When stop codon reaches A site Release factor - Causes addition of water molecule instead of amino acid (ribosome detached from mRNA) Polyribosome - Many ribosomes can translate a single mRNA simultaneously Mutations - Changes in genetic material of cell or virusPoint mutation - Changes just one nucleotide (only affects one protein) Base-pair substitution - Replaces one nucleotide and it's partner with another pair of nucleotides Silent mutation - No effect on amino acid produced Missense mutation - Still code for amino acid, not the correct amino acid though Nonsense mutation - Change amino acid codon into stop codon, resulting in nonfunctional protein