2.1 DNA Structure and Cell
Division
Learning Target:
 5(A) describe the stages of the cell cycle, including
deoxyribonucleic acid (DNA) replication and
mitosis , and the importance of the cell cycle to the
growth of organisms;
Students should know:
 Emphasize that interphase (replication of DNA) is
not part of mitosis, but part of the cell cycle.
 Phases of the cell cycle including interphase, mitosis
(describe the stages), and cytokinesis
 Growth is a function of Mitosis
Vocabulary
 cell cycle
 daughter cells
 Sequence
 DNA
 diploid
 hydrogen bonds
 Replication
 haploid
 Template
 Interphase
 Cytokinesis
 Enzyme
 Mitosis
 Chromosomes
 gene
 Prophase
 Chromatids
 Metaphase
 deoxyribonucleic
 Anaphase
acid
 double helix
 Nucleotide
 Telophase
Types of Nucleic Acids
 DNA – Deoxyribonucleic Acid; two intertwined
strands of genetic information that form a double
helix shape.
 RNA – Ribonucleic Acid; single stranded
instructions used to make proteins
 ATP – Adenosine Triphosphate; high energy
molecule
 ADP – Adenosine Diphosphate; low energy molecule
Thinking Map
 Create a Tree Map on your green
paper classifying the different types
of nucleic acids. – 8 minutes
DNA STRUCTURE
• In 1953, Watson and Crick proposed that DNA is made
of two chains of sugar and phosphate held together by
nitrogenous bases.
• Watson and Crick also proposed that DNA is
shaped like a long zipper that is twisted into a
coil like a spring.
What are the components of DNA?
 Deoxyribose Sugar2
 4 nitrogenous bases3
 Two Purines:
Adenine (A)
 Guanine (G)


Two Pyrimidines:
Cytosine (C)
 Thymine (T)

 Phosphate group1
 Hydrogen Bonds4
1
2
3
4
DNA STURCTURE
The phosphate groups and sugars of the nucleotides
form the backbone of the DNA molecule
“Legs of ladder”
Phosphate &
Sugar Backbone
DNA STURCTURE
The bonds in the backbone between the sugars and
phosphates are covalent bonds
(strong
bonds)
DNA STURCTURE
The nitrogenous bases make up the middle rungs of
the DNA molecule.
“Rungs of ladder”
Nitrogenous
Base (A,T,G or C)
DNA STURCTURE
The bonds between the nitrogenous bases are weak
hydrogen bonds
(indicated by the dotted line)
Thinking Map
Create a Brace Map listing
the components of DNA
5 minutes
What is the difference between a purine and
pyrimidine?
 Purines are double-ringed nitrogenous bases.
 Pyrimidines are single-ringed nitrogenous bases.
How to determine complimentary base pairs, in
DNA?
 In a DNA molecule…
 Adenine bonds with Thymine with two hydrogen bonds
 Guanine bonds with Cytosine with three hydrogen bonds
1.What is the complementary strand for:
ATC GGA TCG
Where is DNA located in a cell?
 In a prokaryotic cell, DNA is usually arranged in a
single circular chromosome that is located in an area
called the nucleoid and may be loosely tethered to
the cell membrane.
 In an eukaryotic cell, DNA is contained within the
nucleus. During some parts of the cell cycle, DNA is
tightly coiled around proteins to form structures
called chromosomes that protect the long, delicate
strands of DNA – typically rod-shaped.