Question

why dna replication not occurs 3' to 5' ?

Answer 1

http://www.ncbi.nlm.nih.gov/books/NBK26850/

go to the section : Only DNA Replication in the 5′-to-3′ Direction Allows Efficient Error Correction

Answer 2

DNA POLYMERASE 3 WHICH IS RESPONSIBLE FOR DNA POLYMERISATION HAS ONLY 5' TO 3' ACTIVITY

Answer 3

Welcome to OpenStudy @sachin12! DNA replication cannot occur in the 3' to 5' direction because DNA polymerase III needs a hydroxyl group for DNA synthesis, so that it can add on nucleotide to grow a complementary DNA strand.

As you can see in the diagram, only the carbon number 3 can provide a hydroxyl group in a nucleotide.