2. What is DNA?
• Found in the nucleus of a cell in two
different structures: chromatin and
chromosomes
• Genetic Material
• Determine inherited characteristics
3. What is the Structure of DNA?
• It looks like a twisted ladder.
• The 2 sides of the DNA ladder are made
up of molecules of sugar (deoxyribose)
and molecules called phosphates.
• The deoxyribose and phosphates
alternate, one followed by the other, all the
way up both sides of the ladder.
5. The Sides of DNA
SIDES
DEOXYRIBOSE
(SUGAR)
RUNGS
PHOSPHATES
6. What are Nitrogen Bases?
• Each rung of the DNA ladder is made up
of a pair nitrogen bases.
• Nitrogen bases are molecules that
contain the element nitrogen combined
with other elements.
• DNA has 4 kinds of nitrogen bases:
adenine (A), thymine (T), guanine (G), and
cytosine (C).
7. The Rungs of DNA
SIDES
DEOXYRIBOSE
(SUGAR)
RUNGS
PHOSPHATES
NITROGEN
BASES
8. How do the Nitrogen Bases Pair?
•
•
•
•
•
ADENINE pairs only with THYMINE.
GUANINE pairs only with CYTOSINE.
A–T
G–C
This pattern of pairing is the key to
understanding how replication works.
10. DNA REPLICATION
• Occurs during the 2nd Phase of
INTERPHASE: Copying of DNA
• It’s so important that we need to talk about
it in detail.
• First let’s look at what DNA looks like…
11. Here is a DNA Molecule
Notice how it is a TWISTED
ladder.
12. What is the Replication Process?
1. The 2 sides of the Parent DNA Molecule
unwind like a zipper unzipping. The ladder
separates between the paired bases.
2. The nitrogen bases that are floating in the
nucleus pair up with the bases on each half of
the Parent DNA molecule to make 2 new
Daughter DNA molecules.
• Because the bases only pair with certain
bases, the order of the bases in the new
Daughter DNA molecules exactly match the
order in the Parent DNA molecule.