Assume That You Grew a Culture of E

question 22

Essay

Assume that you grew a culture of E.coli for many generations in medium containing ¹⁵N (from the ammonium ion),a heavy isotope of nitrogen.You extract DNA from a portion of the culture and determine its density to be 1.723 gm/cm³ (call this sampleA).You then wash the remaining E.coli cells and grow them for one generation in ¹⁴N,extract the DNA from a portion of the culture,and determine its density to be 1.715 gm/cm³ (call this sampleB).You let the culture grow for one more generation in ¹⁴N and extract the DNA (call this sampleC)Each sample of DNA (A,B,and C)is then heated to completely denature the double-stranded structures,cooled quickly (to keep the strands separate),and subjected to ultracentrifugation.Present the centrifugation profiles for heat-denatured DNA (samples A,B,andC)that you would expect.Use the graph below.(Note: Although not the case,assume that single-stranded DNA has the same density as double-stranded DNA.)

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Definitions:

Consolidation Entry G

An accounting entry used in consolidation to eliminate the effects of intercompany transactions among entities within a consolidated group for external reporting.

Wholly Owned Subsidiary

A company whose entire share capital is held by another company, making it a completely controlled entity of the parent company.

Equity Method

An accounting technique used to record investments in other companies, where the investment is initially recorded at cost and adjusted for the investor's share of the investee's profit or loss.

Accumulated Depreciation

The total amount of depreciation expense that has been recorded against an asset since it was acquired and put into use.