1. Which type of recombination occurs between non-identical sequences?
A. Homologous recombination
B. Site-specific recombination
C. Non-homologous recombination
D. Conservative recombination
C. Non-homologous recombination
2. Which statement best describes innate immunity receptors?
A. Highly specific and diverse
B. Encoded directly in the germline
C. Generated by somatic recombination
D. Produced only after infection
B. Encoded directly in the germline
3. The process of generating B and T cell receptor diversity is called:
A. Somatic hypermutation
B. Gene amplification
C. Somatic recombination
D. Antigen drift
C. Somatic recombination
4. Which enzyme adds random nucleotides during junctional diversity?
A. Artemis
B. TdT
C. RAG1
D. RAG2
B. TdT
5. The 12/23 rule ensures:
A. Pairing of identical RSS sequences
B. Random mutation of heavy chains
C. Correct pairing between gene segments
D. Binding of cytokines to receptors
C. Correct pairing between gene segments
6. A defective RAG1/2 complex leads to:
A. Multiple sclerosis
B. Rheumatoid arthritis
C. Severe Combined Immunodeficiency (SCID)
D. Chronic granulomatous disease
C. Severe Combined Immunodeficiency (SCID)
7. What is the purpose of the leader (L) sequence in immunoglobulin genes?
A. Enzyme activation
B. Cell surface expression regulation
C. DNA repair
D. Peptide cleavage
B. Cell surface expression regulation
8. Which chain lacks a D (diversity) region?
A. Heavy chain
B. α chain
C. Light chain
D. β chain
C. Light chain
9. Which molecule cuts open DNA hairpins during recombination?
A. TdT
B. Artemis
C. Tapasin
D. ERAP
B. Artemis
10. What is allelic exclusion?
A. Deletion of one allele for protein balance
B. Preventing rearrangement on the second allele after a productive one
C. Allowing both alleles to express simultaneously
D. Recombination of both heavy chains
B. Preventing rearrangement on the second allele after a productive one
11. The main difference between αβ and γδ T cells is:
A. Their location in the thymus
B. The TCR chains they express
C. The cytokines they release
D. The CD3 molecules they contain
B. The TCR chains they express
12. The CD3 complex is required for:
A. Ligand degradation
B. Transport of TCR to the surface and signal transduction
C. Nucleotide addition
D. Peptide editing
B. Transport of TCR to the surface and signal transduction
13. --Adds random nucleotides to DNA ends
B. TdT
14. --Opens DNA hairpins during recombination
C. Artemis
15. ___ Chooses and recombines gene segments randomly
A. RAG1/2
16. ___ Ensures proper MHC I folding in ER
E. Calnexin
17.___ Trims peptide ends for MHC I loading
F. ERAP
18. ___ Ensures only high-affinity peptides bind to MHC I
D. Tapasin
19. Differentiate between homologous and non-homologous recombination.
Homologous: identical sequences; Non-homologous: non-identical (e.g., site-specific, translocation).
20. Compare receptor specificity and diversity in innate vs adaptive immunity.
Innate = limited/germline; Adaptive = highly specific and diverse.
21. What are the three mechanisms that generate receptor diversity in lymphocytes?
Somatic recombination, combinatorial diversity, junctional diversity
22. Define “recognition signal sequences” (RSS) and describe their components.
RSS = noncoding DNA guiding recombination; includes heptamer, spacer (12 or 23 bp), and nonamer.
23. Explain the 12/23 rule and its biological purpose.
Ensures 12 bp RSS pairs with 23 bp RSS → correct gene segment pairing.
24. Describe how combinatorial diversity contributes to receptor variation.
Random pairing of heavy and light chain variable regions
25. What is junctional diversity, and which enzymes are involved?
Cutting/rejoining DNA segments; uses RAG1/2, TdT, Artemis.
26. Explain the process and purpose of allelic exclusion.
Stops rearrangement on second allele after successful one → ensures one receptor per cell.
27. Compare αβ and γδ T cells in structure and function.
αβ = majority, adaptive response; γδ = minor, innate-like, mucosal surfaces.
28. What are the components and functions of the TCR/CD3 complex?
Components: CD3γ, CD3δ, CD3ε, ζ chain; Functions: transport TCR to surface, signal transduction.