DNA, or deoxyribonucleic acid, is a macromolecule composed of nucleotides that follow specific base pairing rules (A-T, C-G) and exists in a double helix structure. Replication involves the unwinding of the DNA strands and synthesis of new complementary strands, a process facilitated by various enzymes, resulting in semi-conservative replication. Transcription is the process where RNA polymerase synthesizes RNA from the DNA template, culminating in the production of a RNA molecule ready for translation.

1. WHAT IS DNA? Replication and Transcription

2. PEOPLE IMPORTANT TO THE DISCOVERY OF DNA
STRUCTURE
Watson, Crick, & Wilkins were awarded a Nobel Prize because they were the first to make a
model of the double helix shape
Chargaff did experiments to come up with the base pairing rules (A-T, C-G).
Franklin took x-ray pictures of DNA, first to show the shape was a double helix, called image 51

3. DNA STRUCTURE
DNA is a
macromolecule. It is a
type of nucleic acid.
DNA is a polymer (many
units connected to each
other) of nucleotides.
DNA Stands for
Deoxyribonucleic acid.

4. WHAT IS THE MONOMER OF DNA?
DNA is a large molecule made of small parts called nucleotides.
Each nucleotide contains three parts:
1. sugar (deoxyribose)
2. phosphate group
3. nitrogen base (any of 4, adenine, thymine, cytosine or guanine)

5. COMPLEMENTARY BASE PAIRING
DNA has two sides or strands. We say that one strand is
complementary to the other, meaning that they use Chargaff’s base
pairing rule to match up.
Chargaff’s rule states that:
adenine always pairs with thymine (A-T) &
cytosine always pairs with guanine (C-G)
The two strands of DNA are held together by hydrogen bonds.

7. DNA REPLICATION
DNA replication is the process where a molecule of DNA makes
an exact copy of itself. (see foldable model)
DNA "unzips", which means it breaks hydrogen bonds and opens
up.
New nucleotides come in and bond to the open strands using the
base pairing rules.

8. ENZYMES IN DNA REPLICATION
Helicase unwinds
parental double helix
Binding proteins
stabilize separate
strands
DNA polymerase III
binds nucleotides
to form new strands
Ligase joins Okazaki
fragments and seals
other nicks in sugar-
phosphate backbone
Primase adds
short primer
to template strand
DNA polymerase I
(Exonuclease) removes
RNA primer and inserts
the correct bases

9. SEMI-CONSERVATIVE REPLICATION
Each new molecule that results is half "new" and half "old" - this helps minimize mistakes in
copying - we call this semi-conservative replication

10. DNA REPLICATION
Steps of DNA Replication:
1. The parental DNA molecule unwinds and
unzips.
2. Both parental strands serve as templates
for new strands.
3. Free nucleotides link to complementary
bases on each strand.
Two identical DNA molecules result, each
composed of one parental strand, and one new
strand.

18. 1. Initiation:
○ RNA polymerase, the main transcription enzyme, binds to a promoter sequence near the beginning of a
gene.
○ This binding forms a transcription bubble, where the DNA double helix unwinds.
○ One of the exposed DNA strands serves as the template strand for RNA synthesis.
2. Elongation:
○ RNA polymerase moves along the template strand, adding complementary RNA nucleotides.
○ The RNA product is synthesized in the 5’ to 3’ direction.
○ As RNA polymerase advances, the DNA helix re-forms behind it.
3. Termination:
○ Transcription ends when specific sequences in the RNA signal that the transcript is complete.
○ These termination signals prompt RNA polymerase to release the newly formed RNA molecule.
○ The RNA product is now ready for further processing or translation into proteins.
RNA polymerase, the main transcription enzyme, binds to a promoter sequence near the beginning of a
gene.
This binding forms a transcription bubble, where the DNA double helix unwinds.
One of the exposed DNA strands serves as the template strand for RNA synthesis.
RNA polymerase moves along the template strand, adding complementary RNA nucleotides.
The RNA product is synthesized in the 5’ to 3’ direction.
As RNA polymerase advances, the DNA helix re-forms behind it.
Transcription ends when specific sequences in the RNA signal that the transcript is complete.
These termination signals prompt RNA polymerase to release the newly formed RNA molecule.
The RNA product is now ready for further processing or translation into proteins