Question

3. antibody diversity is generated by multiple mechanisms, each of which contributes to the generation of antibodies with a multitude of different amino acid sequences in their antigen-binding sites. several of these mechanisms involve changes in the dna sequences encoding the antibody heavy and light chain proteins. one mechanism that does not rely on changes to the dna within the immunoglobulin heavy and light chain gene loci is, but is instead dependent on:

a) the random usage of kappa light chains vs lambda light chains to pair with the heavy chains

b) the random usage of V,D and J gene segments to form the heavy chain V region sequence

c) the contributions of amino acids from both the heavy chain and the light chain to form the antigen-binding site

d) the fact that heavy chain V regions contain an extra gene segment encoded by the D region compared to the light chain V regions

e) the activity of TdT to add random nucleotides at the juncriins between the V,J, and D region sequences

5. for immunoglobulin heavy and light chain genes, and for tcr beta-chain genes, there are a large number of v gene segments, and relatively few j and/or d segments that rearrange to form the final coding sequence for each gene. the tcr-alpha gene locus is different, and this difference is thought to reflect the fact that nearly all alpha/beta tcrs recognize a peptide bound to an mhc protein. this unique feature of the tcr-alpha locus is:

a) the absence of D gene segements

b) the large sequence sequence distance separating the V-alpha gene segments from the J-alpha gene segments

c) the presence of only five different V-alpha gene segments

d) the presence of two different C-alpha coding sequences

e) the presence of over 60 different J-alpha gene segments

6) some t cells express gamma/delta tcrs rather than an alpha/beta tcr. the organization of the alpha locus helps to ensure that each t cell cannot express both types of tcrs. the mechanism involved is that:

a) the rearrangement of a TCR alpha gene deletes the gamma locus on that allele

b) the rearrangement of a TCR gamma gene deletes the alpha locus on that allele

c) the gamma/delta TCR signals the T cells to delete the alpha gene locus

d) the RAG recombinase enzymes are down-regulated immediately after the firsr TCR genes rearrange

e) the alpha/beta TCR signals the T cell to delete the gamma gene locus

Answer 1

Answer 3:

Antibody structure consists of light and heavy chains. Light chain has a single variable and a single constant domain. On the other hand.heavy chain has a variable domain, three constant regions and one J region-for joining upper two domains to the two lower domains of heavy chain.

Antibody diversity is created via DNA associated changes, and other mechanism involves rearrangement of genes for constant region, J region and variable region. Hence correct choice should be :

one mechanism that does not rely on changes to the dna within the immunoglobulin heavy and light chain gene loci is, but is instead dependent on

b) the random usage of V,D and J gene segments to form the heavy chain V region sequence.