How would they identify a suspect as being guilty of committing a crime? [By comparing their DNA to samples found at the scene.]
Why does that work? How could they tell whether or not someone was at the scene, by only looking at and comparing DNA? [Each person’s DNA is different, so this provides scientific evidence that the person was at the scene.]
Today, we’re going to talk about the technology available for isolating and analyzing DNA.
Procedure:
1. Begin teacher-led discussion, reviewing gene mutations (see above Do Now):
i. Germ cell mutations: Occurs in an organism’s gametes; can be passed to offspring if mutated germ cell is fertilized.
ii. Somatic cell mutations: Occurs in an organism’s body cells and can affect the
organism; can’t be passed to offspring (Ex: skin cancers, leukemia).
iii. Review deletions & insertions (frame shift mutations) and substitution: which
are all point mutations.
2. Activity: Chart- Review on types of Mutations (see above Do Now).
3. Begin teacher led discussion on DNA technology (Making a DNA Fingerprint) p. 243:
i. PCR (polymerase chain reaction): Quickly makes copies of certain parts of DNA.
a. The number of DNA copied doubles every 5 minutes.
ii. RFLP Analysis (restriction fragment length polymorphism): Takes DNA from
blood or tissue samples & cuts them into many fragments, using restriction enzymes.
a. restriction enzymes: Bacterial enzymes that cut DNA at a specific sequence.
iii. Gel Electrophoresis: (p. 244) Separate nucleic acids or proteins by size and charge.
iv. Probes: Radioactive (so, will “glow” under UV light); Bind to selected DNA
fragments, and allows a picture to be taken; thus creating the DNA fingerprint.
(5 minutes)
4. Activity: Allow students to make a “review book” & and present their creations to the class.
i. Guide the students through folding the paper to make their books.
ii. Give them options on how they could organize the content into the books.
iii. Give them time to decorate the books & present them, individually, to the class.
5. Closure
(25 minutes total)
Closure:
So, the types of technology available for DNA analysis are PCR- which makes many copies of DNA, RFLP- which cuts DNA into fragments using restriction enzymes, and gel electrophoresis- which separates proteins and nucleic acids by size and charge, and probes- which makes the selected DNA “glow”, making a genetic fingerprint.
(5 minutes)
Assessment/ Evaluation:
Objective(s):
Distinguish between the types of technology available for amplifying, isolating,
and analyzing DNA (DOK 2 Biology, 5.c).
Informal: The teacher will assist the students in making a review booklet (M),
with definitions of each technology, along with the materials needed to perform
each technology (C).
Formal:
The teacher will check the students’ review booklets for accuracy of the
aforementioned content (C), and will record a “complete” grade in the grade book (D).
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