MIT Department of Biology 7.014 Introductory Biology, Spring 2005 Recitation Section 20 April 25-26, 2005 Immunology A. Antibody production Shown below is a schematic of the production of a heavy chain polypeptide for an antibody. At the top is the chromosomal arrangement found in an immature B cell, at the bottom is shown the heavy chain polypeptide. V segments D segments J segments constant segment = intron regions 1. Label the process indicated by each arrow. Choose the one best option for each from: protein processing transcription translation transduction DNA ligation DNA rearrangement RNA splicing RNA ligation 2. Indicate on the diagram below where you would expect to find each of the following components: promoter Transcription terminator start codon stop codon 3. Indicate on the diagram below the variable and the constant region of the heavy chain polypeptide. 1An activated B cell undergoes cell division and produces many daughter cells. Some daughter cells will function as B cells, some will function as plasma cells and other will become memory cells. 4. Assume that an activated B cell undergos somatic mutation and produces two different B cells each with a slightly altered version of the antibody. This event occurs early in the immune response (i.e. when antigen was present in the organism). Mutation A makes the antibody-antigen interaction stronger, mutation B makes the antibody-antigen interaction much weaker. i) Would you expect memory cells derived from the original activated B cell? __ __ ii) Would you expect memory cells derived from the daughter B cell with mutation A (antibody-antigen interaction stronger)? __ __ iii) Would you expect memory cells derived from the daughter B cell with mutation B (antibody-antigen interaction much weaker)? __ __ Explain your answers. B. Immunology and Immunizations The varicella zoster virus (VZV) is the infectious agent that results in chickenpox, a common childhood illness that causes itchy red spots on the skin. Contracting VZV as a child is relatively benign, but can present serious health issues when contracted as an adult. 1. How does a VZV infected cell signal the immune system? How are the infected cells specifically eliminated from the body? 2. Over the course of a lifetime, the average person is exposed to VZV many times, yet usually only displays symptoms once. What is the immune system mechanism that results in lifetime resistance? As of September 1999 any child entering kindergarten must have had chickenpox or received a new vaccine against VZV. 3. Present an argument in support of this vaccination campaign. 4. Present an argument opposed to this vaccination campaign. 2C. Immunology and Central Dogma (phosphorylcholine). N O OHO O P + CH 3 CH 3 CH 3 CH2 CH2 _ _ Arg 52 Tyr 33 Glu 58 Glu 35 Trp 104 Heavy Chain of antibody Asn 90 Phosphorylcholine Shown below is a diagram of the interaction of an antibody molecule with an antigen 1. Indicate the strongest type of interaction that occurs between the amino acids listed and the Phosphorylcholine molecule. Phosphorylcholine and Arg 52 Phosphorylcholine and Tyr 33 Phosphorylcholine and Glu 35 Phosphorylcholine and Trp 104 2. Each of the following mutations alters the binding of the antigen to the antibody. Explain in terms of the change in interactions why the binding of the Phosphorylcholine to the antibody has remained the same, been made stronger, or been made weaker. mutation in antibody binding of antibody to phosphorylcholine 1 Trp 104 -----> Leu 104 same 2 Arg 52 -----> Lys 52 stronger 3 Glu 35 -----> Gln 35 weaker 4 Tyr 33 -----> Phe 33 weaker 3. Can any of these mutations be due to a single base pair substitution? If so, give one possibility. 3------------The Genetic Code U C A G U UUU phe UUC phe UUA leu UUG leu UCU UCC UCA UCG ser ser ser ser UAU tyr UAC tyr UAA STOP UAG STOP UGU cys UGC cys UGA STOP UGG trp U C A G C CUU leu CUC leu CUA leu CUG leu CCU CCC CCA CCG pro pro pro pro CAU his CAC his CAA gln CAG gln CGU arg CGC arg CGA arg CGG arg U C A G A AUU ile AUC ile AUA ile AUG met ACU ACC ACA ACG thr thr thr thr AAU asn AAC asn AAA lys AAG lys AGU ser AGC ser AGA arg AGG arg U C A G G GUU val GUC val GUA val GUG val GCU GCC GCA GCG ala ala ala ala GAU asp GAC asp GAA glu GAG glu GGU gly GGC gly GGA gly GGG gly U C A G STRUCTURES OF AMINO ACIDS at pH 7.0-OO -OOO C O OO COC H CO H C CH3 H C CH2CH2CH2 C H C CH2 CNH2 H C CH2N -C NH3 NH3 NH3 NH2 NH3 O + + NH2+ + ALANINE ARGININE + ASPARAGINE ASPARTIC ACID (ala) (arg) (asN) (asp) O O O C O OO O O CCO COC H C CH2CH2 C H C HH C CH2 SH H C CH2CH2 - NH3 NH3 O NH3 NH2 NH3 ++ ++ CYSTEINE GLUTAMIC ACID GLUTAMINE GLYCINE (cys) (glu) (glN) (gly) --OHO OO O O O O + H C HCHCNC C +H C C CH2CH3 H C CH2 C CH3 H C CH2CH2CH2CH2 NH3H C CH2 N NH3 CH3 NH3 CH3 NH3NH3 C H++ + + H ISOLEUCINE LEUCINE LYSINE HISTIDINE (ile) (leu) (lys) (his) OH H OO C OOO O O CC C H C CH2CH2 S CH3 H C CH2 CH 2HH C H C CH2 OH NH3 NH3 CH2 NH3 ++ H N + CH2 + METHIONINE H H H (met) PHENYLALANINE PROLINE SERINE (phe) (pro) (ser) -HHO O -OH H O --ONOO OC CC H H C CH2C CH HCC CH3 NH3 CH 3 OH H C C + H C CH2 CH 3NH 3 NH3 HNH3 OH ++ H H+HH VALINE THREONINE TRYPTOPHAN H TYROSINE (val)(thr) (trp) (tyr)
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