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?

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.  

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