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My Cou O d. the time required to replicate the chromosome from the origin to the

ID: 194675 • Letter: M

Question

My Cou O d. the time required to replicate the chromosome from the origin to the terminus. e. the time required for the number of cells to double. Question 2 Not yet answered Marked out of 1.oo P Flag question Assume that the potato salad left out on the picnic table contains 50 Salmonella cells. Assuming these cells have a 30 minute generation time, how many cells will there be when the picnic is cleaned up 8 hours later? If you are having trouble with this question, Bacteria Number of Cells tot cerur ations of initia O Type here to search

Explanation / Answer

Ans. Method 1: Cellular growth kinetics follows first order kinetics.

ln ([A]t / [A]0) = kt                 -equation 1

where, [A]t = Final number of cells

            [A]0 = Initial number of cells (in inoculum)

            k = specific growth rate = 0.693 / g

            t = growth

            generation time, g = 0.693 / k

Given,

            Doubling or generation time, g = 30 min = (30/60) hr = 0.50 hr

            [A]0 = 50 cells

Putting the values in equation 1-

            ln ([A]t / 50) = (0.693 / 0.50 hr) x 8 hr

            Or, 2.303 log ([A]t / 50) = 1.386 hr-1 x 8 hr

            Or, log ([A]t / 50) = 11.088 / 2.303 = 4.8146

            Or, log [A]t – 1.699 = 4.8146

            Or, [A]t = antilog (4.8146 + 1.699) = antilog 6.5136

            Hence, [A]t = 3.263 x 106

Therefore, number of cells after 8 hours = 3.263 x 106

# Method 2:             Nt = N0 (2)n              - equation 1

            Where, n = number of generation.

# Number of generations, n = Growth time / generation time

                                                = 8 hr / 30 min

                                                = (8 hr x 60 min hr-1)

                                                = 16

Putting the values in equation 2-

            Nt= 50 x (2)16 = 3276800

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