Question

DNA replication always proceeds in only one direction because the ________ of the incoming nucleotide is attached to the free ________ of the growing DNA strand.

5'-deoxyribose / 3'-base
5'-phosphate / 3'-hydroxyl
3'-phosphate / 5'-hydroxyl
3'-base / 5'-deoxyribose

Answer 1

In DNA replication, the incoming nucleotide's 5'-phosphate is attached to the free 3'-hydroxyl of the growing DNA strand, allowing replication to proceed only in one direction.

Step-by-step explanation:

DNA replication always proceeds in only one direction because the 5'-phosphate of the incoming nucleotide is attached to the free 3'-hydroxyl of the growing DNA strand. During the process of DNA replication, DNA polymerase can only add nucleotides to the 3' end of the newly forming strand, building in a 5' to 3' direction. This is due to the enzyme's requirement for a free 3'-OH group for the addition of nucleotides, creating an elongating DNA strand that grows as a new phosphodiester bond is formed between the 3'-OH end of one nucleotide and the 5' phosphate of the next.

The reason DNA replication proceeds only in one direction is because the 5'-phosphate of the incoming nucleotide is attached to the free 3'-hydroxyl of the growing DNA strand.