Course Home session.masteringbiology.com Online Final Item 109 previous | 109 of
ID: 100432 • Letter: C
Question
Course Home session.masteringbiology.com Online Final Item 109 previous | 109 of 125 next Item 109 Long-lived memory cells generated in the primary response to antigen A give rise to a heightened secondary response to the same antigen, but they do not affect the primary response to a different antigen (B). Primary immune response to antigen A produces Secondary immune response to antigen A produces antibodies to A primary immune response to antigen s to A. antibodies to B Part A To answer the following question, assume that the number of B cels producing a specific antibody is proportional to the concentration of that antibody 104 103 On day 16, assume that one out of every 10% B cells in the body is specific for antigen A and that the antibody concentration on day 16 is about 2 × 101 Antibodies to A 102 101 10° Antibodies to to B Calculate the frequency of B cells specific for antigen A on day 36 if the antibody concentration on day 36 is about 8 × 10, (For practice doing calculations with proportions, try this exercise. For practice doing calculations with numbers written in scientific notation, try this exercise.) 0 7 14 21 28 35 42 49 56 Exposure to Time (days) O 1 in 105 O 1 in 400 O 1 in 250 1 in 20 Exposure to antigen A antigens A and B © Pearson Education, Inc. Submit My Answers Give Up 120. Item 120 1 ptExplanation / Answer
Ans- on 16 day
Frequency of b cell for A antigen- 1 out of (10) 5 I.e. 1 out of 100000.
Total no of A antigen on that day- 2*(10) 1 I.e 20
So total no of b cells- 20*100000= 2000000
On 36 day
The no of antigen - 8* (10)3 I.e. 8000
The frequency of b cells- total no of b cells/ no of antigen
= 2000000/8000= 250
So the frequency will be 1 in 250