Gen Bio I BIO 101

1. BIOL 101
GENERAL BIOLOGY I
LAB #3
Isolation of DNA from
Wheat Germ

2. WHAT IS DNA?
WHERE IS IT LOCATED IN A CELL?
Instructions providing all of the information necessary for
a living organism to grow and live reside in the nucleus of
every cell
These instructions tell the cell what role it will play in
your body
Found in the nucleus of eukaryotic cells and in the nucleoid region of prokaryotic
cells

3. 3
DNA is the hereditary material in humans
and almost all other organisms
DNA is like a large
recipe book that
determines all of the
characteristics that
are specific to
individual organisms

4. 4
DNA Is Found in all Living Organisms
The germ is the
embryo or sprouting
section of the seed.

5. DNA = GENETIC INFORMATION
Chromosomes = condensed (coiled) threadlike structures
of DNA and associated proteins
Chromatin = DNA & associated proteins in a
dispersed, rather than condensed state

6. DNA is composed of 4 nucleotides
Each nucleotide consists of…
Nitrogenous
Base
Phosphate
group
Sugar
HOW CAN A MOLECULE HOLD INFORMATION?

7. DNA HAS 4 NITROGENOUS BASES
Adenine
Cytosine
Thymine
Guanine

8. RUNGS OF LADDER CONSIST OF PAIRED NITROGENOUS BASES
Complementary base pairing rules:
Adenine (A) pairs only with thymine (T)
Cytosine (C) pairs only with guanine (G)
Each pair of bases
held together by
hydrogen bonds

9. HOW CAN ONLY 4 LETTERS TELL THE CELL
WHAT TO DO?
The DNA strand is made of letters
The letters make words
The words make sentences
These “sentences” are called genes.
Genes tell the cell to make other molecules called
proteins and proteins enable a cell to perform special
functions.

10. WHY ISOLATE DNA?
Genetic Testing
Body Identification
Analysis of forensic evidence

11. INTRODUCE AND PERFORM DNA
EXTRACTION PROTOCOL

12. ISOLATION OF PLANT DNA:
USING WHEAT GERM
 Wheat germ is the DNA source in this protocol.
 Comes from wheat seeds.
 The "germ" is the embryo, which is the part of the seed that can
grow into a new wheat plant.

13. EXTRACTING THE DNA:
WHY USE HOT WATER?
Heat softens the cellulose in the cell wall that
surrounds the plant cell.
The cell wall is the first barrier that keeps us from
getting to the DNA.
The grinding of the wheat germ in the mortar, with the
pestle, also helps to physically break down the cell wall
so that we can more easily get to the DNA inside the
nucleus.

14. EXTRACTING THE DNA:
WHY USE DETERGENT?
 Detergent contains sodium laurel sulfate, which cleans dishes by
removing fats and proteins.
 It acts the same way in the DNA extraction protocol, pulling
apart the fats (lipids) and proteins that make up the membranes
surrounding the cell and nucleus.
 The plasma membrane as well as the nuclear membrane are the
remaining barriers that keep us from getting to the DNA inside
the nucleus.
Both soap and grease molecules organize themselves in bubbles
(spheres) with the more polar heads outside to face the water and
hydrophobic tails inside to hide from the water

15. WHY USE DETERGENT?
When detergent comes close to the cell, it captures the
lipids and proteins and releases the DNA.

16. EXTRACTING THE DNA:
WHY USE MEAT TENDERIZER?
 Cells contain enzymes called DNA-ase and endonuclease in their
cytoplasm.
 These are proteins which cut apart DNA into such small fragments that
the fragments would not be visible.
 Meat tenderizer contains proteases such as papain and substilisin. A
protease is an enzyme that breaks apart the peptide bonds between amino
acids in proteins and denatures them.
 Denatured enzymes lose their 3-D shape, and thus become inactive.
 Enzymes also denature at 60° Celsius, and DNA denatures at 80° Celsius.
This is why we use hot water in this extraction protocol, but not boiling
water.

17. The DNA released from the cell nucleus is dissolved
in the water/detergent/wheat germ solution and
cannot be seen because this solution is polar.
DNA precipitates out of solution in alcohol, a more
nonpolar solvent.
Besides allowing us to see the DNA, the alcohol
separates the DNA from the other cell components,
which are left behind in the water solution.
EXTRACTING THE DNA:
WHY USE ALCOHOL?

18. DISCUSS GENETIC
MODIFICATION OF DNA

19. GENETIC INFORMATION ENCODED IN EXACT
SEQUENCE OF BASES
Genome - an organism’s complete set of DNA
Gene – segment of DNA with instructions for producing a particular
protein (polypeptide)
Human genome consists
of 20,000–25,000 genes
Humans are identical in
99.9% of the sequences of
their genes

20. 20
Small Sections of DNA are Called
Genes
Genes are like the
ingredients that are needed
to make up each individual
recipe

21. HOW DOES DNA DIRECT CELLULAR ACTIVITIES?
 DNA codes for mRNA, which codes for proteins
 Proteins play structural or functional roles in cells
In next week’s lab we will study the processes of transcription and translation!!

22. 22
Biotechnology: organisms, cells, and their
molecules are modified to achieve practical
benefits
Genetic Engineering: Adding, deleting, or transplanting genes from
one organism to another, to alter the organisms in useful ways
Agriculture Human Health

23. 23
Because the genetic code is universal, genes
of one organism can be expressed in
another organism

24. 24
Insect Resistance

25. ALMOST EVERYONE IN THE UNITED STATES
CONSUMES GENETICALLY MODIFIED FOODS
REGULARLY WITHOUT KNOWING IT.
25
Genetically modified crops in the U.S. are insect and herbicide resistant!

26. FEARS AND RISKS:
ARE GENETICALLY
MODIFIED FOODS
SAFE?
26
This new breed had
the desired trait but
also exhibited
undesirable traits.