Question

Another step in PCR requires small single-stranded DNA primers to anneal to a target sequence on denatured DNA. Two primers are used. Ideally these primers will have similar melting temperatures. The melting temperature is defined as the temperature at which 50% of the DNA is in the single-stranded form. Which of the following primers will have the highest melting temperature?
A. GGGGAAATTTCCCC.
B. AAAAGGGCCCTTTT.
C. AAAAGGCCTTTT.
D. GGGAAATTTCCC.

Answer 1

Answer:

A. GGGGAAATTTCCCC.

Explanation:

When calculating the melting temperature in the DNA primers, we use the formula:

( 2 × ( A + T ) ) + ( 4 × ( G + C ) )

From the above formula; it is obvious that G and C have a greater tendency of participation when determining which DNA primers that have the highest melting temperature.

A.  GGGGAAATTTCCCC = 8

B. AAAAGGGCCCTTTT   = 6

C. AAAAGGCCTTTT        = 4

D. GGGAAATTTCCC        = 6

From the given options, we can see that option A have the highest component of G and C.