DNA Replication
Each time a new cell is made, the cell must receive an exact copy of the parent cell DNA. The new cells then receive
the instructions and information needed to function. The process of copying DNA is called replication. Replication
occurs in a unique way – instead of copying a complete new strand of DNA, the process “saves” or conserves one of
the original strand. For this reason, replication is called semi-conservative. When the DNA is ready to copy, the
molecule “unzips” itself and new nucleotides are added to each side.
1. The first step in the process of DNA Replication begins with ________________ breaking the ___________
bonds between the bases and unzipping the helix.
The __________ enzyme begins to unwind the DNA at the ____________________. This is a specific site on
the DNA.
The helicase enzyme moves in both directions from the _________________, forming a ______________. At
either end is a _____________________, a Y-shaped region where the new strands of DNA are elongating.
2. Single stranded _________________ react with the single-stranded regions on the DNA and __________ the
unwound DNA
3. An _________________, called a ___________ constructs an RNA primer, a sequence of about _________
nucleotides, complementary to the parent DNA. (Remember base pairing)
4. ________________ is the major enzyme involved in DNA replication. The enzyme adds
___________________ to the RNA primer.
Energy is required for the bonding to take place. The nucleotides arrive as _________. The DNA bases have
a ___________ sequence. DNA bases arrive with their own __________ as they are bonded by DNA
polymerase III.
DNA polymerase III can only add a nucleotide to the ________ end of a pre-existing chain of nucleotides and
cannot initiate a nucleotide chain. Therefore the new DNA strand grows from ______ to ______.
Parent strands are ___________. Leading strand is replicated from _____ to ______ while the laggin strand
is replicated from _____ to _____
When replication occurs on the laggings strand the DNA polymerase III reaches ____________ it is replaced
by _______________. At this point the RNA is removed and replaced by _______. The enzyme _______
attached to the DNA strand to form ________________ bonds. New primers are made a a new _________
is put into place.
