One primer attaches to the __ end of the gene region on the 5' to 3' strand, another to the ___ end of the gene region of the 3'
to 5' strand. This was maybe not explicit in the video. 3’ and 5’ refer to the orientation of the DNA strand. The 3’ end is the end that has the OH group used for adding new nucleotides. The 5’ end is the end where a phosphate sticks out from the ribose. The two strands that make up the DNA molecule run anti parallel to each other. Synthesis is always in the 5’ to 3’ direction (because that is where new nucleotides attach), and the template strand is read 3’ to 5’ (because it runs antiparallel).
This question is incomplete however during DNA amplification using polymerase chain reaction, <u>the two primers attach to each DNA strand at the 3' end</u>.
Two primers are used during this process; one primer each for the two complementary strands of DNA (that run antiparallel to each other). The 5' end of each primer is attached to the 3' end of each DNA strand regardless of the direction the strand is running (5' to 3' or 3' to 5'). This process of attaching the primers to the DNA strand is known as annealing.
