Question

What happens when a dideoxynucleotide is added to a developing DNA strand?

a) DNA strand elongation stops
b) DNA polymerase is activated
c) DNA helicase unwinds the double helix
d) RNA primers are synthesized

Answer 1

The addition of a dideoxynucleotide to a developing DNA strand results in the termination of strand elongation, as it lacks the necessary 3'-hydroxyl group for further nucleotide additions. This mechanism is utilized in Sanger sequencing to determine DNA sequences.

Step-by-step explanation:

When a dideoxynucleotide is added to a developing DNA strand, it results in the termination of the strand elongation. This is because dideoxynucleotides lack the 3'-hydroxyl group essential for forming a phosphodiester bond with the next nucleotide, thus preventing any further addition of nucleotides to the growing DNA strand. In Sanger sequencing, this principle is exploited to synthesize DNA fragments of varying lengths, each ending with a dideoxynucleotide, which can then be used to determine the DNA sequence.