試題詳解

26. Bacteria are grown in isotopic ¹⁵N (heavy) medium and then transferred to ¹⁴N (light) medium and allowed to replicate for 2 generations. The DNA is subsequently isolated and centrifuged in a CsCl₂ gradient to yield what type of gradient band(s)?
(A)One heavy and one half-heavy band.
(B) One light and one half-heavy band.
(C) One half-heavy (intermediate to heavy and light) band.
(D)One heavy band.
(E)One light band.