Essential Cell Biology Exam 1 Questions with Complete Solutions

alternative splicing - ANSWER-Splicing of RNA transcripts from the same gene in different ways, each of which produces a distinct protein. aminoacyl-tRNA synthetase - ANSWER-Enzyme that attaches the correct amino acid to a tRNA molecule to form an aminoacyl-tRNA. anticodon - ANSWER-Sequence of three nucleotides in a transfer RNA molecule that is complementary to the three-nucleotide codon on a messenger RNA molecule; each anticodon is matched to a specific amino acid covalently attached elsewhere on the transfer RNA molecule. codon - ANSWER-Sequence of three nucleotides in a DNA or messenger RNA molecule that represents the instruction for incorporation of a specific amino acid into a growing polypeptide chain. exon - ANSWER-Segment of a eucaryotic gene that is transcribed into RNA and expressed; dictates the amino acid sequence of part of a protein. gene expression - ANSWER-The process by which a gene makes its effect on a cell or organism by directing the synthesis of a protein or an RNA molecule with a characteristic activity. genetic code - ANSWER-Set of rules specifying the correspondence between nucleotide triplets (codons) in DNA or RNA and amino acids in proteins. general transcription factors - ANSWER-Proteins that assemble on the promoters of many eucaryotic genes near the start site of transcription and load the RNA polymerase in the correct position. initiator tRNA - ANSWER-Special tRNA that initiates translation. It always carries the amino acid and methionine. intron - ANSWER-Noncoding region of a eucaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing to produce mRNA. messenger RNA (mRNA) - ANSWER-RNA molecule that specifies the amino acid sequence of a protein. Produced by RNA splicing (in eucaryotes) from a large RNA molecule made by RNA polymerase as a complementary copy of DNA. It is translated into protein in a process catalyzed by ribosomes.