The Integumentary System
More Than Skin Deep
Cell Cycle
TAKS
• TAKS Objective 2 – The student will
demonstrate an understanding of
living systems and the environment.
TEKS
• The student knows the structures and functions
of nucleic acids in the mechanisms of genetics.
The student is expected to
(A)describe components of
deoxyribonucleic acid (DNA); and illustrate
how information fro specifying traits of an
organism is carried in the DNA;
(B)explain replication, transcription, and
translation using models of DNA and ribonucleic
acid
Engage
• Humans shed their
•
entire epidermis every
15 to 30 days.
Bloodhounds detect
this upon tracking
Explore 1: Cell Cycle Research
• Student will complete a cell cycle diagram
with detailed description of cellular activity
in each of the cell cycle phases.
Cell Cycle
Explain: Cell Cycle
• All cells constantly replace themselves by
a process called mitosis, which is a small
section of the cell cycle.
• New skin cells push the older generation
of cells toward the surface of the skin,
where they are finally shed as a flake-like,
lifeless, residue
What are the two main phases of the cell cycle?
Cell Cycle
includes
G1 phase
Interphase
M phase
(Mitosis)
is divided into
is divided into
S phase
G2 phase
Prophase
Metaphase
Anaphase
Telophase
The Cell Cycle?
Cell cycle - changes a cell goes
through during its life span.
contains 2 main steps.



1.Interphase (LONGEST phase of the
cell cycle and has three parts)




G1 (Everyday Cellular Activity)
S (DNA Synthesis)
G2 (Other Organelles Replicated)
2. M-Phase or Mitotic Phase (Shortest
phase)


Mitosis (Nuclear Division)
Cytokinesis (Cytoplasm Division)
Explore 2: S Phase
Berry Full of DNA Lab
Photo 51

Scientific contributions to the discovery
of the DNA structure.
Review: Interphase (G1)
•
•
•
•
•
•
What is the main purpose of a cell that is in G1?
G1 Phase: During this stage the cell is carrying on
its everyday activities.
If the cell’s surface to volume ratio gets too big
then the cell must get ready to divide.
Do some cells entering a resting state?
What is this phase called?
G0 Phase: Resting State - Some cells leave the
cell cycle and stay here much longer than others
ex) brain, nerve, etc…
Section 12-1
Explain: DNA
Nucleotides
Purines
Adenine
Guanine
Phosphate
group
Pyrimidines
Cytosine
Thymine
Deoxyribose
Section 12-1
Structure of DNA
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
DNA


Deoxyribose Sugar
Base Pairs
A-T

Phosphate
G-C
What is a Nucleotide?
The basic building block of nucleic acids
containing a sugar, base, and a
phosphate.
P
B
S
S = Deoxyribose Sugar or Ribose Sugar
B = Adenine, Guanine, Cytosine, Thymine or Uracil
P = Phosphate
Sugar
Bases
(Nitrogenous Bases)

These chemicals are often called nitrogenous bases
because of the high content of nitrogen (N) atoms
Purines
Pyrimidines



1) Cytosine (C)
2) Thymine (T)
3) Uracil (U)
Phosphate
Nucleotide


The Sugar and the Phosphate make up the
backbone of the structure
The bases make up the rungs of the ladder
Different Types of Nucleotides in
DNA
Deoxy---Adenine
Deoxy----Thymine
|
|
P
P
Deoxy---Cytosine Deoxy----Guanine
|
|
P
P
Many Nucleotides Together
Parts of DNA and RNA





Have a
Sugar/Phosphate
Backbone
Bases make up the
steps of the ladder
A-T---DNA
A-U---RNA
G-C---DNA & RNA
DNA Structure
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Practice

On your paper, complete the missing
DNA strand by adding the
complementary bases.

ATCGTTGCCATC
TAGCAACGGTAG

DNA Replication
A Closer Look
»
»
»
»
DNA before replication: 1 double helix
»
DNA after replication: 2 identical double
helixes
»
Section 12-2
DNA Replication
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Original
strand
Nitrogenous
bases
Getting Ready
Step 1
Unwinding and Unzipping
Unwind and Unzip
Helicase Enzyme
Step 2
Separates
Polymerase Enzyme
Step 3
Picking up Complementary Bases
Separation and Adding Bases
5’----3’
Step 4
Rewind
Two New DNA Molecules
• Each DNA Molecule with a Parent and Daughter Strand
Interphase (G2)
•
G2 phase: The rest of the cell’s
organelles are reproduced.
Elaborate: DNA Jewelry