Question

You want to amplify the DNA between the two stretches of sequence shown below. Of the listed primer pairs, choose the correct pair that will allow you to amplify the DNA by PCR. 5'-ACATTACCAA----GACCTGCTTT-3' 3' -TGTAATGGTT----CTGGACGAAA-5' 5' -TGTAATGGTT-3' and 5'-TTTCGTCCAG-3' O 5'-ACATTACCAA-3' and 5'-AAAGCAGGTC-3' 5'-TGTAATGGTT-3' and 5'-CTGGACGAAA-3' O 5'-AACCATTACA-3' and 5'-CTGGACGAAA-3'

Answer 1

Answer:

PCR primers are generally used at the ends of DNA strand to amplify the region of interest.

Here the region of interest is

                5'- ACATTACCAA----GACCTGCTTT-3'

                3'- TGTAATGGTT----CTGGACGAAA-5'

To amplify DNA region by PCR, DNA polymerase enzyme is required. This polymerase has a property of adding free nucleotides to the 3'end of the DNA. And it requires primers as they can only add nucleotides to a pre existing 3'-OH group.

Now lets look at our DNA strand.

In the top strand, 5'- ACATTACCAA----GACCTGCTTT-3',

5'- ACATTACCAA can be used as a primer.

                                5'- ACATTACCAA........................... (nucleotides will be incorporated here)

                              3'- TGTAATGGTT----CTGGACGAAA-5'

In the bottom strand, 3'- TGTAATGGTT----CTGGACGAAA-5'

5'- AAAGCAGGTC can be used as a primer.

                                  5'- ACATTACCAA----GACCTGCTTT-3'

(nucleotides will be incorporated here) ..............................CTGGACGAAA-5'

So the correct pair of primer is 5'- ACATTACCAA -3' and 5'- AAAGCAGGTC- 3' .