Question

What would be the result of an experiment if the primers had a melting temperature of 50 degress celcius if they orignally had a melting temperature greater than or equal to 78 degrees celcius?

Answer 1

Answer:-
The melting temperature controls the binding of the primers to your template DNA. By defintion, at melting temperature 50% of the primer molecules are bound to their corresponding target sequence. If the difference in melting temperature between the two primers is too high, it might be difficult to find experimental conditions where both primers can bind to their target.
Melting temperature can be calculated by a vast array of software using very differents algorithms and their results can differ, even if applied to the same base sequence. There are whole philosophies about how to calculate melting temperature in the most realistic way. As a rule of thumb, for primers up to 20 bases in lenght, take 2°C for each A or T and 4°C for each C or G. This will be accurate enough for many cases.
I once had to use primer pairs where some software gave me a difference in melting temperature of 20°C. These were primers targeted to the exact 5'- and 3'-end of an open reading frame and it was necessary to include restriction sites at each of the primers' 5'-ends. So there was very little to no room for varying primer sequence. Luckily, the method was successful anyway, I got the desired DNA amplification.