PCR Controls

This section provides a comprehensive guide to PCR. It also includes guidelines and suggestions for maximizing results from your PCR.

The photograph of one of Dr. Adlard’s polymerase chain reaction (PCR) experiment results compares amplified DNA
of bivalve parasites Marteilia Sydney and its close relative Marteilia refringent. The same primers were used, with the DNA of bivalve hosts and parasites mixed as part of the same PCR experiment. Look at the photograph can you see differences between these parasite species? Both positive and negative controls are used in PCR experiments.

The positive control, a known sample of parasite DNA, shows that the primers have attached to the DNA strand. The negative control, a sample without DNA, shows if contamination of the PCR experiment with foreign DNA has occurred. The reference DNA ladder contains a mixture of pieces of DNA. So, the DNA of M.sydneyi will always show up in the same region on agar, when compared to this ladder.

Data Analysis:

Consider the following results of PCR testing of oysters from southeast Australian estuaries.

(a) Which sites have infected oysters?

Explain your answer.

(b) Match the following estuaries to the PCR testing sites:

  • Shoalhaven and Crookhaven
  • southern Moreton Bay
  • Georges River
  • Clarence River.

Refer to evidence to justify your answers.

(c) Is there any evidence that the primers used amplified the bivalve DNA? Comment fully.

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