Cell bio exam 2| 162 questions| with complete solutions

What are the primary functions of the 5' cap and poly A tail? correct answer Increase the stability of the mRNA;Facilitate mRNA export from the nucleus to the cytoplasm; What are nuclear pore complexes (NPCs) and what do they do? correct answer provide access to the nucleus and regulate the transport of proteins and RNA across the nuclear envelope. What is required for an mRNA to be considered export ready? correct answer must be bound to a specific set of proteins: Poly-A-Binding Proteins, A cap-binding complex, proteins that mark completed RNA splices, nuclear transport receptor Why is translation not a direct one to one correspondence between a single nucleotide on the mRNA and single amino acid in a protein? correct answer there are only 4 different nucleotides in mRNA and 20 different types of amino acids in a protein How many consecutive nucleotides in an in an mRNA make up a codon? correct answer three How is the genetic code redundant? correct answer some amino acids are specified by more than one codon How many codons specify one amino acid? correct answer 64 codons for 20 amino acids What role do transfer RNAs play in translation? correct answer molecular adaptors that match amino acids with codons How do tRNAs function as adaptor molecules? correct answer they recognize and bind codon at one site on their surface and to the amino acid on the other site what is an anticodon? correct answer a set of three consecutive nucleotides that pair with the complementary codon in an mRNA molecule how do aminoacyl-tRNA synthetases couple tRNAs to the correct amino acid? correct answer different synthetase enzyme for each amino acid. Enzyme attaches amino acid to 3' end on tRNA. Step 1: Amino acid is activated through linkage of carboxyl group to AMP Step 2: AMP-linked carboxyl group on amino acid is transferred to hydroxyl group on sugar at 3' end of tRNA molecule What role do ribosomes (rRNA) play in