3). While exploring the Enchanted Forest you stumble across a species of fairies
ID: 199521 • Letter: 3
Question
3). While exploring the Enchanted Forest you stumble across a species of fairies called Pucks. You somehow managed to obtain some tissue samples from them and sequence their genome. You find that Pucks have similar organization of immunoglobulin lg genes as humans. They have heavy chains but only one type of light chain and no pseudo-genes. a). Pucks have 20 Vh gene segments, 5 DH gene segments, 4 JH gene segments, 5 CH gene segments, 10 VL gene segments, 5 J gene segments, and 2 CL gene segments. Taking into account only combinatorial joining of gene segments and gene association of heavy and light chains, how many different antibody specificities can Pucks potentially generate? Show your work. (1 point) b). You find cells in the peripheral blood of Pucks that are similar to human B cells When you sequenced the lg genes of this population of mature naïive B cells you found more diversity that what you calculated in part a. Drawing from your knowledge of how humans generate antibody diversity, what other mechanisms could have contributed to the diversity of Puck immunoglobulins? Provide a brief description of all the various ways/mechanisms that could generate diversity other than the combinatorial diversity discussed in part a. Include the following elements in your answer for each: 1). Whether it occurs during B cell development or following antigen activation of B cells. 2). Briefly describe how the mechanism contributes to diversity 3) state which lg chains (heavy and/or light) are affected and 4). Which CDR(s) of the lg heavy and/or chains is/are affected. (3 points) c). From your sequencing analysis of B cells in Pucks you find the following sequence for an lg-light chain rearrangement coding joint. TGCACTAG ACGTGATC Which mammalian lg diversity-generating mechanism would also produce such a sequence? Explain your answer. (1 point)Explanation / Answer
a) heavy chains = 20*5*4*5 = 2000
light chains = 10*5*2= 100
Total diversity= 200,000
b) two other mechanisms are 1) junctional and insertional diversification and 2) somatic hypermutation
During the joining of different gene segments a variable number of nucleotides are more than often lost from the ends of the recombinig gene segments or a nucleotide is inserted. this loss or gain of the nucleotides at the recombining site is called junctional divrsification. Because of this antibody show greatest variations at junctions of V and C regions that forms CDR3. Somatic hypermutation occurs after the antigen stimulation in the variable region of both heavy and light chains. The DNA of the B-cells during development is susceptible to a high rate of somatic mutation making the variable region more different increasing the diversity.
c) combinatorial
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.