Question

Chipmunk mitochondrial DNA was fingerprinted using the single primer amplified region technique (SPAR) and the PCR reaction. One four base primer was used. If the DNA from chipmunk mitochondria is a circlular piece of DNA about 16000 base pairs long, how many fragments should be produced by this technique?

Answer 1

Answer:

The correct answer is about 63 fragments.

Explanation:

As mentioned in the question, there are four base pairs in a primer. So, let us consider the sequence of the primer to be 3'-ATGC-5'. Hence, the primer would complementarily combine to the sequence 5'-TAGC-3', and will carry on with the work of adding nucleotides.  

Now, the probability of the appearance of TACG, that is, any four base sequence will be,  

Probability of T will be 1/4 due to the presence of four different nucleotides.  

Similarly, the probability of the bases A, C and G will also be 1/4.  

Therefore, the probability of the four base sequence will be 1/4 * 1/4 * 1/4 * 1/4 = 1/256

Now, as the length of the base pairs sequence is 16000, therefore, the number of the given four base sequence will be 16000/256 = 62.5.  

Hence, about 63 distinct fragments would be produced.