Question

Here is the nucleotide sequence of one strand of a fragment of double-stranded DNA, which will be amplified by PCR using short primers:

     5' TGGCAGTCGATGCTGCTAGCTGGCCTTGAGTCGTGC 3'     

Primers that could be used to amplify this entire DNA fragment are:

A) 5’ GACTGCCA 3’ & 5’ GCACGACT 3’

B) 5’ GACTGCCA 3’ & 5’ AGTCGTGC 3’

C) 5’ TGGCAGTC 3’ & 5’ GCACGACT 3’

D) 5’ TGGCAGTC 3’ & 5’ AGTCGTGC 3’

E) 5’ TGGCAGTC 3’ & 5’ CGTGCTGA 3’

Answer 1

Ans - Option C) 5’ TGGCAGTC 3’ & 5’ GCACGACT 3’ is correct.

PCR primers are short pieces of single-stranded DNA, usually around 202020 nucleotides in length. Two primers are used in each PCR reaction, and they are designed so that they flank the target region (region that should be copied). That is, they are given sequences that will make them bind to opposite strands of the template DNA, just at the edges of the region to be copied. The primers bind to the template by complementary base pairing.

5' TGGCAGTCGATGCTGCTAGCTGGCCTTGAGTCGTGC 3'     

3' ACCGTCAGCTACGACGATCGACCGGAACTCAGCACG 5'

Primer works in 3' to 5' direction

For above DNA primer formed will be

PRIMER 5' GCACGACT 3' for 5' TGGCAGTCGATGCTGCTAGCTGGCCTTGAGTCGTGC 3'     

Primer 5' TGGCAGTC 3' for 3' ACCGTCAGCTACGACGATCGACCGGAACTCAGCACG 5'