Final answer:
The primer sequences for PCR amplification are 5'-ctagggttccgcatCtcaattgacatggac-3' (top) and 5'-gtccatgtcaattgaGatgcggaaccctag-3' (bottom), written in the 5' to 3' direction and designed to be complementary to the target DNA strands for amplifying a specific region.
Step-by-step explanation:
The student has asked for the sequence of 20-nucleotide primers to be used for PCR to amplify a specific region within a given DNA sequence. The top primer sequence, complementary to the bottom strand, is 5'-ctagggttccgcatCtcaattgacatggac-3', and the bottom primer sequence, complementary to the top strand, is 5'-gtccatgtcaattgaGatgcggaaccctag-3'.
These primers are chosen to flank the region of interest, allowing for amplification of the desired segment during repeated cycles of PCR. Primers must be complementary to their target DNA sequences to ensure proper annealing during the PCR process. When designing primers, always write sequences in the 5' to 3' direction to align with DNA synthesis by DNA polymerase.
Finally, it is essential to remember that complementary DNA strands are always antiparallel, with one strand running in the 5' to 3' direction and the other in the 3' to 5' direction, but the sequence of the primer itself is written from the 5' to 3' end, which is the direction of synthesis.