2. DNA Structure
DNA Stands for
Deoxyribonucleic acid.
DNA is a macromolecule.
It is a type of nucleic
acid. DNA is a polymer
(many units connected
to each other) of
nucleotides.
3. 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
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.
6.
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. 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
9. 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.
10. 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
11.
12.
13.
14.
15.
16. 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
