BIOC20 LECTURE 7 EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED

BIOC20 LECTURE 7 EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED What type of viruses are picorna, flavi and toga viruses? +ssRNA. What is the structure of picornaviruses? Small, naked (non-enveloped) capsid, linear genome. How do picornaviruses bind to cellular receptors? Depressions or loop regions on the surface. How many copies of VP do mature virions contain? 60. Instead of the 5' cap, what do picornaviruses have? They have VPg attached covalently to the 5' end. What do VP 1-3 do in picornaviruses? What about VP4? VP 1-3 form the capsid shell, VP4 is embedded within the shell. Explain the following figure of picornaviruses: P1 = Structure. P2, P3 = non-structural. What is the IRES? Internal ribosome entry site, on the 5' non-coding region, allows the initiation of translation without having a 5' cap, translation can happen internally, away from the 5' end, contains extensive secondary and tertiary structures. What structure do picornavirus VP1-4 fold into? Jelly roll, composed on an 8-stranded B-barrel. What type of virus is polio? Picornavirus. How does polio RNA enter into the cytoplasm? Major rearrangement of proteins, conformational change in VP1, end terminal inserts itself into the membrane, creates a pore where RNA can now insert, then genome is taken up by endocytosis, acidic pore created, genome goes through. What mechanism do most cellular RNAs use for translation near their 5' end? Cap-dependent mechanism, eIF (eukaryotic initiation factors) form the complex, and recruit 40S, which scans for start codon AUG, then 60S binds, 80S complex forms, translation begins. What are the S numbers in proteins of picornaviruses? S is their sedimentation coefficient.