Antibody Genes Flashcards
Genes for immunoglobulins are unlike other human genes in that
a. each polypeptide chain is encoded by several exons.
b. Ig genes are composed of introns and exons
c. somatic recombination occurs before mRNA is transcribed
d. there is less Ig genetic material in mature B cells than in other somatic cells
e. both c and d are true.
e. both c and d are true.
The gene segments needed to encode the variable region of a k chain are
a. one Jk plus one Dk.
b. one Jk plus one Ck.
c. one Vk plus one Dk.
d. one Vk plus one Jk.
e. one Vk plus one Jk plus one Dk.
d. one Vk plus one Jk.
Pseudogenes are DNA sequences which look very similar to functional genes except for the presence of a(n)
a. intron.
b. leader sequence.
c. promoter codon.
d. signal sequence.
e. stop codon.
e. stop codon.
Combinatorial diversity says that by random combination of 40 functional Vk segments with five Jk segments, the number of possible different k chains that could be made are
a. 40.
b. 45.
c. 70.
d. 200.
e. 1200.
d. 200.
Which does NOT contribute to Ig antigen-binding diversity
a. Any L chain can combine with any H chain to form a functional antibody.
b. Any Vk can be joined to any Jk to encode the light chain V region.
c. Many CH genes are present in the germline DNA.
d. Random numbers of N nucleotides can be added during somatic recombination.
e. VJL and VDJH joining is imprecise.
c. Many CH genes are present in the germline DNA.
The proper joining of one VL to one JL is regulated by
a. heptamer and nonamer sequences.
b. leader sequences.
c. P-nucleotide addition sites.
d. 12 and 23 nucleotide spacers between heptamer and nonamer sequences.
e. TdT binding site for DNA.
d. 12 and 23 nucleotide spacers between heptamer and nonamer sequences.
Since each B cell productively rearranges a single H and L chain allele, it exhibits
a. affinity.
b. allelic exclusion
c. antibody restriction.
d. antigen-binding diversity.
e. cross-reactivity
b. allelic exclusion
Primary mRNA for H chain encodes
a. one VH, one DH, and one JH segment.
b. one VH, one DH, and multiple JH segments.
c. multiple VH, one DH, and one JH segments.
d. multiple VH, one DH, and multiple JH segments.
e. multiple VH, DH, and JH segments.
b. one VH, one DH, and multiple JH segments.
Somatic recombination occurs
a. in the bone marrow stem cell.
b. in the progenitor cell as it is becoming a B cell.
c. in the mature B cell following antigen contact.
d. in the plasma cell after antigen contact.
e. in the plasma cell after antibody secretion.
b. in the progenitor cell as it is becoming a B cell.
Junctional diversity affects primarily the amino acid sequence in
a. all CDR equally.
b. CDR1.
c. CDR2.
d. CDR3.
e. FR3.
d. CDR3.
Isotype switching
a. changes the leader sequence exon so the antibody is secreted.
b. improves the antigen binding specificity of an Ig molecule.
c. increases the affinity of antibodies in a process called affinity maturation.
d. increases the functional diversity of Ig molecules.
e. occurs randomly between switch regions.
d. increases the functional diversity of Ig molecules.
Isotype switching resembles somatic recombination because both processes
a. are catalyzed by the products of RAG1 and RAG2
b. are regulated by helper T cell cytokines.
c. can result in stop codons in coding sequences.
d. occur in developing B cells in the bone marrow.
e. result in the irreversible loss of DNA from the B cell.
e. result in the irreversible loss of DNA from the B cell.
Alternative mRNA splicing
a. allows the B cell to improve its antigen-binding fit after antigen contact.
b. allows the B cell to make membrane IgM from the mature mRNA for secreted IgD.
c. can be used for the simultaneous production of any two Ig isotypes.
d. is a process by which a B cell can simultaneously synthesize m and d chains.
e. occurs in response to T cell cytokines.
d. is a process by which a B cell can simultaneously synthesize m and d chains.
Because of the order of the CH gene segments (Cm, Cd, Cg3, Cg1, pseudogene Ce, Ca1, Cg2, Cg4, Ce, and Ca2), a human B cell which undergoes isotype switching from IgM to IgG1 can never in the future secrete
a. IgA.
b. IgE.
c. IgG2.
d. IgG3.
e. IgG4.
d. IgG3.
Isotype switching is always productive because
a. B cells produce all isotypes simultaneously.
b. isotype switching does not involve recombination of DNA gene segments.
c. no DNA is deleted from the chromosome in isotype switching.
d. no effector diversity results from isotype switching.
e. recombination between switch sites occurs in introns so it cannot introduce stop codons into coding regions.
e. recombination between switch sites occurs in introns so it cannot introduce stop codons into coding regions.
