CECsci.138


TITLE:    How Cells Duplicate and Why
          Where Something Can Go Wrong

AUTHOR:   Judy A. Grunke, Weiser Junior High,
          Weiser, Idaho

GRADE LEVEL/SUBJECT:  7;  Life Science (2-week unit)

OVERVIEW:  Cells are the basic unit of function and
structure in living things.  After students have learned
cell parts and organization, they are introduced to cell
division.  Understanding the role of deoxyribonucleic acid
(DNA), and how and why it must replicate, is essential to
comprehending how our genetic patterns are transmitted to
new cells.  Constructing a three-dimensional model of the
DNA molecule enhances the students' discernment.

PURPOSE:  Genes are the small heredity units on chromosomes
and are made of DNA molecules.  Before a cell divides, the
DNA must replicate so that the two new cells will each have
the organism's genetic code.  If foreign materials invade
the cell while the DNA is duplicating, they may be
incorporated into the molecule.  If these miscoded cells are
not killed by the body's own defense systems, they will
multiply and could take over, disrupting the cell's normal
activities or dividing rapidly and erratically, crowding out
the normal cells.  It is important to understand the
construction of the DNA molecules; how and why they divide;
how good nutrition and personal habits can help maintain the
genetic code.

OBJECTIVE(s):
1.   The learner will be able to define pertinent
     vocabulary.
2.   The learner will be able to describe the DNA molecule,
     its construction, how it replicates.
3.   The learner will be able to discuss why good nutrition
     is essential for proper DNA duplication.
4.   The learner will be able to explain how, when, a
     carcinogen may be incorporated into the DNA molecule.
5.   The learner will demonstrate his/her understanding of
     the DNA molecule by constructing one from chenille
     pieces.

RESOURCES/MATERIALS:
Provided:  textbook, paper, pencils, (colored pencils are
           excellent)
Needed:    Film: "The Intricate Cell", American Cancer
           Society, Boise, ID
For Lab:   6 pieces chenille per student (2 the same
               color, 1 each of 4 different colors)
           wire cutters or sharp scissors

ACTIVITIES AND PROCEDURES:

                            SET

Models of a cell undergoing mitosis.  A model of a DNA
molecule.

                    INSTRUCTIONAL INPUT

VOCABULARY:
deoxyribonucleic acid, DNA, gene, chromosome, replicate,
mitosis, nutrients, carcinogen

REVIEW:
Nutrients, food containing them.
Protein contains nitrogen, an essential ingredient in the
     DNA molecule.
Mitosis--interphase, when the DNA replicates.

DISCUSS:
How DNA molecules are constructed; when and how the DNA
molecule makes a copy.

FILM:  "The Intricate Cell"
Observe cells undergoing mitosis and the construction of DNA
     molecules.
Discuss the causes of 80% of cancers--industrial pollutants,
     overexposure to the sun, cigarette smoke.
Discern how and when cancer-causing agents can disrupt DNA's
     replication.

                      GUIDED PRACTICE
TEXTBOOK:  vocabulary and study questions
CLASS NOTES
LAB:  Construct a DNA molecule

                    INDEPENDENT PRACTICE
Quiz, Text

TYING IT ALL TOGETHER:  Deoxyribonucleic acid (DNA) is the
molecule which contains our genetic codes.  The DNA must
copy itself before the cell divides so the daughter cells
will get the code.  The cell has to have the proper
nutrients in the right amounts so that the DNA can
replicate.  If carcinogens are in the cells when the DNA is
duplicating, they may be incorporated into the DNA molecule.
Cigarette smoke contains known cancer-causing materials.  We
have control over 80% of known carcinogens.