DNA: THE BLUEPRINT OF LIFE
Deoxyribonucleic Acid (DNA): The basic molecule of heredity which stores
and passes on genetic information from one generation to the next.
FACT or FICTION??? Every human has a unique set of DNA?
FICTION! Identical Twins have the same DNA
Connections: What organelle in a plant or animal cell contains DNA?
NUCLEUS
STRUCTURE OF DNA:
NUCLEOTIDE: are the repeating parts or building blocks that make up
DNA.
Each NUCLEOTIDE is made of 3 things:
1. 5 CARBON SUGAR (DEOXIRIBOSE)
2. PHOSPHATE GROUP
3. NITROGEN BASE (THE ONE THING THAT CAN BE DIFFERENT )
The 4 NITROGEN BASES ARE:
a. ADENINE (A)
b. THYMINE (T)
c. GUANINE (G)
d. CYTOSINE (C)
How do NITROGEN BASES BOND?
ADENINE and THYMINE
GUANINE and CYTOSINE
The SHAPE of the DNA molecule looks like a “twisted ladder” and is called the
DOUBLE HELIX
COOL FACT: The DOUBLE HELIX was first discovered by James Watson and
Francis Crick in 1953.
Diagram of a NUCLEOTIDE
2. Phosphate Group
P
N
3. Nitrogen Base
(Can be A,T,G,or C)
1. 5 Carbon Sugar
(Deoxiribose)
Think About It!: How many nucleotides are in the nucleus of one human cell?
5 BILLION
The DNA MOLECULE is made of TWO strands of nucleotides attached to
each other.
How are the NUCLEOTIDES attached?
PHOSPHATE-SUGAR: bonds keep one entire strand together (similar to the
side rails of a ladder).
NITROGEN BASE: bonds hold the two strands together (similar to the rungs,
or steps, of a ladder).
WHAT IS THE FUNCTION OF DNA?
THE SEQUENCE OR ORDER OF THE NUCLEOTIDES IN A DNA MOLECULE
IS THE CODE FOR MAKING ALL OF THE SPECIFIC PROTEINS FOR AN
ORGANISM AND FOR HOW GENES WILL BE CONTROLLED. (i.e. DNA
HOLDS THE INSTRUCTIONS FOR HOW TO MAKE PROTEINS AND HOW
GENES ARE CONTROLLED.)
DNA Molecule Diagram
P
A
T
P
Phosphate-Sugar
Bond
One
Nucleotide
P
C
G
P
Nitrogen Base
Bond
COOL FACT: The information stored in a DNA molecule from one human
cell would fill a book with approximately 500,000 pages!!!!!
DNA REPLICATION:
DNA REPLICATION: :is the process by which DNA makes a copy of itself.
Replication occurs during the INTERPHASE stage of the Cell Cycle.DNA
replication in a human cell takes about 6 hours.
Connections: Why does DNA replication occurs just before cell division?
Each new cell will need an exact copy of the DNA. During
Mitosis, when the nucleus is copied, the copies of DNA will be
distributed to the new daughter cells.
STEPS IN DNA REPLICATION:
1. DNA HELICASE (enzyme) “UNZIP” the DNA molecule. The nitrogen
base bonds are broken and the two strands of nucleotides separate.
2. Unpaired NUCLEOTIDES bond with the MATCHING nucleotides on the
separated strands.
3. DNA POLYMERASE (enzyme) helps form PHOSPHATE-SUGAR bonds
that link the new nucleotides together. Two identical DNA molecules are
created.
RELATIONSHIP ANALOGY FOR UNDERSTANDING DNA REPLICATION
Step 1 DNA “unzips (two people break up)
DNA Helicase: (is like the major fight that is the reason for the break up)
Step 2 Bonding of unpaired nucleotides with matching nucleotides (is like
meeting someone new)
Step 3 Phosphate-Sugar bonds form (is like the marriage between two people)
DNA Polymerase: (is like true love which is the reason for the marriage)