Download File - Dixie Middle School Science

DNA and
Bioethics
HERSHEY AND CHASE
• Virus -made of DNA and protein
• The experiments
• a virus with either radioactive DNA
or radioactive protein were used to
infect bacteria
• Either the radioactive proteins or
radioactive DNA would be
transferred to the bacteria
• Identifying which one is transferred
would identify the genetic material.
• Only the radioactively labeled DNA
was transferred.
DNA STRUCTURE
• Composed of nucleotides
• nitrogen containing base, a five -carbon sugar (deoxyribose), and a phosphate
group.
•
Four possible bases: adenine (A), guanine (G), cytosine (C), or thymine (T)
CHARGAFF’S RULES
1st: The composition of DNA varied from one species to another.
This molecular diversity added evidence that DNA could be the genetic material.
2nd: the amount of one base always approximately equals the amount of a particular
second base.
Example: guanines equals the number of cytosines
BASE PAIRING
• Purines- Adenine and guanine
• two ring structures.
• Pyrimidines- Thymine and cytosine
• one ring structure.
•
A purine always combines with a pyrimidine in the DNA double helix!
THE DOUBLE HELIX
• Rosalind Franklin
• Worked with DNA fibers.
• Maurice Wilkins, used x-ray diffraction photographic techniques to
analyze the structure of DNA.
In February 1953, Francis Crick and James D. Watson had started
to build a model of DNA.
• indirectly obtained Franklin's data which had crucial information
•
Crick and Watson then published
their double helical model of DNA!
(They get most of the credit)
Watson
and
Crick
RNA
DNA
Single Stranded
Double Stranded
Specific Base
Uracil
Thymine
Sugar
Ribose
Deoxyribose
Size
Relatively small
Big (chromosomes)
Location
Moves to cytoplasm
Stays in Nucleus
Types
mRNA, tRNA, rRNA
DNA
The completion of The Human Genome
Project! WOW!!!!!
 However, is knowing all of our DNA a good
thing?
Imagine someone analyzes
part of your DNA. Who
controls that information?
 What if your health
insurance company found
out you were predisposed
to develop a devastating
genetic disease. Might they
decide to cancel your
insurance? Privacy issues
concerning genetic
information is an important
issue in this day and age.
 ELSI stands for Ethical,
Legal and Social Issues.
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Who owns genetically modified organisms such as
bacteria?
Can such organisms be patented like inventions?
Are genetically modified foods safe to eat? Might they
have unknown harmful effects on the people who
consume them?
Are genetically engineered crops safe for the
environment?
Might they harm other organisms or even entire
ecosystems?
Who controls a person’s genetic information? What
safeguards ensure that the information is kept
private?
How far should we go to ensure that children are free
of mutations? Should a pregnancy be ended if the
fetus has a mutation for a serious genetic disorder?
A strain of corn has been created with a gene that
encodes a natural pesticide. On the positive side,
the transgenic corn is not eaten by insects, so
there is more corn for people to eat. The corn also
doesn’t need to be sprayed with chemical
pesticides, which can harm people and other living
things. On the negative side, the transgenic corn
has been shown to cross-pollinate nearby
milkweed plants. Offspring of the cross-pollinated
milkweed plants are now known to be toxic to
monarch butterfly caterpillars that depend on
them for food. Scientists are concerned that this
may threaten the monarch species as well as other
species that normally eat monarchs