DNA replication summary notes
15 November 2022 17:00
Theories of DNA replication
Proved wrong:
Conservative- one daughter cell retains both strands of the original, the other gets both stra
the copy
Dispersive- DNA molecule splits into individual nucleotides with extra nucleotides, two new
molecules formed
Thought to be correct:
Semi conservative- the original molecule is split into two strands, each strand is matched to
strand, so each daughter cell's DNA has one strand of the original and one strand of the copy
Semi conservative replication
1. Double helix unwinds as hydrogen bonds between bases are broken by DNA helicase
happens in one region of the molecule at a time-whole of DNA does not unwind
simultaneously- unwinds in one direction but DNA strands are antiparallel so DNA poly
has to work in opposite directions
2. Leading strand- copied continuously by DNA polymerase that adds nucleotides to exist
end with hydrogen bonding between bases. Joins the nucleotides with phosphodiester
Free floating nucleotides are complimentary to existing nucleotides and the bases on t
nucleotides on the template strand.
3. Lagging strand- DNA polymerase builds short sections called Okazaki fragments as DNA
polymerase can only add nucleotides to an existing 3' end so must keep detaching and
reattaching to the strand. Joins the nucleotides with phosphodiester bonds. DNA ligase
the Okazaki fragments with phosphodiester bonds. Free floating nucleotides that are a
to parental strand are complimentary to the bases on the existing nucleotides of the te
strand.
4. Original strands of DNA act as template for synthesis of new strands- each molecule of
made up of one parent strand and one new daughter strand
Unwound region called the replication fork
Unwound strands called parental strands, free floating nucleotides are attracted to pare
15 November 2022 17:00
Theories of DNA replication
Proved wrong:
Conservative- one daughter cell retains both strands of the original, the other gets both stra
the copy
Dispersive- DNA molecule splits into individual nucleotides with extra nucleotides, two new
molecules formed
Thought to be correct:
Semi conservative- the original molecule is split into two strands, each strand is matched to
strand, so each daughter cell's DNA has one strand of the original and one strand of the copy
Semi conservative replication
1. Double helix unwinds as hydrogen bonds between bases are broken by DNA helicase
happens in one region of the molecule at a time-whole of DNA does not unwind
simultaneously- unwinds in one direction but DNA strands are antiparallel so DNA poly
has to work in opposite directions
2. Leading strand- copied continuously by DNA polymerase that adds nucleotides to exist
end with hydrogen bonding between bases. Joins the nucleotides with phosphodiester
Free floating nucleotides are complimentary to existing nucleotides and the bases on t
nucleotides on the template strand.
3. Lagging strand- DNA polymerase builds short sections called Okazaki fragments as DNA
polymerase can only add nucleotides to an existing 3' end so must keep detaching and
reattaching to the strand. Joins the nucleotides with phosphodiester bonds. DNA ligase
the Okazaki fragments with phosphodiester bonds. Free floating nucleotides that are a
to parental strand are complimentary to the bases on the existing nucleotides of the te
strand.
4. Original strands of DNA act as template for synthesis of new strands- each molecule of
made up of one parent strand and one new daughter strand
Unwound region called the replication fork
Unwound strands called parental strands, free floating nucleotides are attracted to pare
