Dna Synthesis Direction Information

Synthesis Direction of DNA - When DNA is synthesized, the free 3´ hydroxyl (OH) group from the growing strand of DNA attacks the phosphate on the next base to be added. When a cell divides, it passes on genetic information by producing copies of its DNA. Chemists have also learned to copy DNA. In the journal Angewandte Chemie, a German team has now introduced a new copying technique that uses a single strand of DNA as the “master copy”, like a cell, but does not require enzymes.

Pyrophosphate is released and the new base forms a phosphodiester bond with the growing strand of DNA. The free 3´ hydroxyl group is then freed to attack the next base to be added.

Within a cell, the DNA double strand is separated in segments during the copying process. One of the single strands serves as the “master copy” or template. Polymerase enzymes snap together the corresponding nucleotides stepwise to form the new complementary strand, beginning with a “starting segment” known as a primer. The backbone of a DNA strand is an alternating chain of five-membered sugar rings and phosphate groups. The chain links are formed at the 3’ and 5’ oxygen atoms of the sugars; natural growth occurs in the 3’ direction.

Look the video of DNA synthesis direction - 3' or 5'

Because the strands of a DNA double helix have opposite chemical polarity, one strand is extended in a 5'-3' direction while the other extends in a 3'-5' direction. However, DNA polymerases can only catalyze synthesis in the 5'-3' direction.

Extending both ways synthesis direction

Extending both ways: A method for DNA-templated synthesis on solid support is described. Controlled, stepwise chain extension was demonstrated both in the direction favored by nature (3′-extension; see scheme) and in the direction typical for conventional DNA synthesizers (5′-extension).

Source : http://library.thinkquest.org/C006188/basics/replication.htm

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