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5.1 Immunogenetics: Generation of Diversity β Test 1
Q1. The enormous diversity of antibodies is generated mainly by:β Somatic rearrangement of germline gene segments
Q2. The heavy-chain variable region is assembled from which gene segments?β V, D and J segments
Q3. The light-chain variable region is assembled from:β V and J segments only
Q4. Combinatorial diversity refers to:β Different combinations of V, (D) and J segments and of heavy/light chains
Q5. Junctional diversity is generated at the joints between segments by:β Imprecise joining, nucleotide addition (TdT) and removal
Q6. Somatic hypermutation, which further diversifies antibodies after antigen exposure, occurs in the:β Germinal centres of secondary lymphoid organs
Q7. The enzymes that initiate V(D)J recombination are:β RAG-1 and RAG-2
Q8. The 12/23 rule in V(D)J recombination ensures that:β Segments join only in the correct, productive order
Q9. Allelic exclusion ensures that a single B cell expresses:β Antibody from only one of the two parental alleles (one specificity)
Q10. Terminal deoxynucleotidyl transferase (TdT) contributes to diversity by:β Adding non-templated (N) nucleotides at segment junctions
Q11. The 'one cellβone antibody' rule means that each mature B cell:β Produces antibody of a single specificity
Q12. The genetic basis of antibody diversity was established by the somatic recombination work of:β Susumu Tonegawa
Q13. Compared with combinatorial diversity, junctional diversity primarily increases variability in the:β CDR3 region
Q14. Recombination signal sequences (RSS) are recognised by RAG and consist of:β Conserved heptamer and nonamer separated by a 12- or 23-bp spacer
Q15. P-nucleotides arise during V(D)J recombination from:β Opening of hairpin DNA intermediates
Q16. Class switch recombination changes the antibody's constant region and is therefore part of:β Functional diversity (effector function), not specificity
Q17. The major sources of antibody diversity include all of the following EXCEPT:β Reverse transcription of antibody mRNA
Q18. Failure of productive rearrangement on both alleles of a chain typically results in:β Apoptosis of the developing lymphocyte
Q19. The diversity of the T-cell receptor is generated by mechanisms that are:β Largely analogous to antibody V(D)J recombination (but without somatic hypermutation)
Q20. The large diversity of Ξ±Ξ² T-cell receptors is generated mainly by:β Combinatorial joining of VΞ±/JΞ± and VΞ²/DΞ²/JΞ² gene segments
Q21. Match each diversity mechanism with its description and select the correct option.β A-iii, B-iv, C-i, D-ii