WWLPT

"Fishing for Microsatellites"|

PCR Demo

Put your goggles on now that the 90 seconds is complete, transfer the Styrofoam float with the DNA sample to the 54^oC water bath with tongs and leave it in this water bath for 90 seconds.  Take the goggles off.

Discussion

Again prompt your students to hypothesize what might be happening in the Eppendorf and to the DNA pictured on the board.  You may be able to redirect hypotheses generated by students in the last round for the purpose of deducing the importance of this step.  In the end, lead them to the fact that the lower temperature causes the primers in the Eppendorf to ‘Anneal’ to the separated strands of DNA.

Students will undoubted ask why the primers bonds with the DNA, or why don’t the DNA strands just come back together.  These questions should lead to a review discussion of the function of primers, etc…

Chalkboard

Draw the primers in their appropriate places.  One should be positioned at somewhere to the upstream end of the 5’ to 3’ strand of DNA (but not at the end), while the other is positioned at the downstream end of the 3’ to 5’ strand of DNA (but not at the end).

5’ ATCGCTTACGTCAACT 3’        original strand
                               AGTT      5’         primer

5’      CGCT                             3’       primer
3’ TAGCGAATGCAGTTGA 5’        original strand

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