Download File

Deoxyribonucleic Acid (DNA)
Synthesis
Soriano
Parts Involved
DNA Parent Strand
Daughter Strands
Extra Nucleotides
RNA primers
Helicase
Primase
Polymerase III
Polymerase I
Ligase
Start
Helicase unwinds DNA and
unzips the DNA strands by
breaking the hydrogen bonds
between the nitrogenous
bases
Since polymerase III cannot
begin the synthesis of a
polynucleotide, Primase must
first add a primer, made of
RNA nucleotides, to the origin
of replication
Extra nucleotides spontaneously
form hydrogen bonds with the
unbound bases of the parental
strands. Extending from the 3’
end of the RNA primer,
Polymerase III covalently bonds
the extra nucleotides creating
the leading strands.
Since polymerase III can’t
bond new nucleotides to the 5’
end of the RNA primer, more
primers must be added by
primase to begin the formation
of the lagging strands
Polymerase III covalently bonds
the sugar-phosphate backbones
of the newly hydrogen bonded
nucleotides for each of the
Okazaki fragments which
creates the lagging strands
Polymerase I replaces the RNA
primer with DNA nucleotides
Ligase covalently bonds the
gaps between the Okazaki
fragments of the lagging strands
DNA synthesis yields 2 DNA strands:
each consisting of 1 daughter strand
and 1 parent strand.