Biotechnology

AP Biology· difficulty 3/5

Two samples are amplified by quantitative PCR. Sample 1 crosses the fluorescence threshold at cycle 18, while Sample 2 crosses at cycle 26.

Cycle Fluorescence Sample 1 Sample 2

A lower Cq (cycle quantification) for Sample 1 versus Sample 2 indicates:

  • A

    Sample 2 lacked DNA polymerase.

  • B

    Sample 1 had more starting template than Sample 2.

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  • C

    Sample 1 had less starting template than Sample 2.

  • D

    Both samples had identical template amounts.

Explanation

Cq is the cycle at which fluorescence crosses threshold. More starting template reaches threshold sooner (lower Cq); thus Sample 1 has higher initial template than Sample 2.

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