Meselson and Stahlʹs Experiments Involved Growing E

question 12

Multiple Choice

Meselson and Stahlʹs experiments involved growing E. coli on a medium containing ¹⁵N heavy nitrogen) which increased the density of the bacterial DNA. Cells were then grown on a medium containing only ¹⁴N. DNA samples were obtained for analysis after one, two and three rounds of replication generations) and centrifuged on a density gradient. The double-helical DNA forms bands in the gradient depending on its density. How many bands did Meselson and Stahl see after two generation of cells were grown on the ¹⁴N medium?

• A) One with DNA containing both ¹⁵N and ¹⁴N.
• B) Two, one with DNA containing only ¹⁵N and one with DNA containing only ¹⁴N.
• C) Two, one with DNA containing both ¹⁵N and ¹⁴N and one with DNA containing only 14_N.
• D) Three, one with DNA containing only ¹⁵N, one with DNA containing both ¹⁵N and ¹⁴N and one with DNA containing only ¹⁴N.

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Definitions:

Long-term Debt

Borrowings and financial obligations that are due to be repaid over a period longer than one year.

Financing Activities

Transactions that result in changes in the size and composition of the equity and borrowings of a company.

Cash Flow Statement

A financial statement that shows how changes in balance sheet accounts and income affect cash and cash equivalents, breaking the analysis down to operating, investing, and financing activities.

Investing Section

A part of a company's cash flow statement that shows the cash spent on or generated from investment activities, such as purchasing physical assets or securities.