Download Faculty of Education Abridged Lesson Plan

Mini-1
Subject / Course: Science
Grade Level: Grade 6
Topic: DNA ISOLATION
TC Name: Ms Sayer
Date: 2011-2012 school year
Duration of lesson: 50 minutes
1. Objectives and Skills
1.
Students will be able to identify the component molecules of DNA.
2. Students will be able to Construct a model of the DNA double-helix.
.
2. Materials
1. One slightly overripe banana
2. Dishsoap (the clearer the better)
3. Table salt 99% rubbing alcohol (ask at the pharmacy counter for 99% isopropanol)
4. One coffee filter
5. One elastic band
6. One small dish
7. One fork
8. One measuring cup
9. One clear cup (coffee cup size)
10. One small clear cup (a shot glass or champagne flute works very well)
11. Small beads
12. Pipecleaners
3. Activities
Explain to the students that we are going to talk about DNA and how DNA has revolutionized crime
scene investigations.
Part A: What is DNA?
Explain to students that each cell in all living organisms contains DNA. In plants and animals that DNA
is contained in a nucleus. This DNA has two main purposes: 1. It serves to store and pass down the
biological characteristics of any living thing. 2. It controls / dictates everything that goes on in the
cells of a living being. This includes producing both functional and structural proteins.
-When this long, skinny DNA molecule is all coiled up and bunched together it is called a chromosome.
-Each chromosome is a separate piece of DNA, so a cell with eight chromosomes has eight long pieces
of DNA.
-A gene is a segment of the long DNA molecule. Different genes may be different lengths. Each gene
is a code for how a certain molecule in the cell should be made.
Explain to the students that you are going to create a chain of DNA out of beads and pipe cleaners.
Step 1 Choose your large beads for the sugar and phosphate molecules that make up the backbone.
You will need 26 beads of 2 different colors for a total of 52 beads. Color the key on your DNA
Guide.
Step 2 Choose your small beads for the nitrogen bases. You will need 6 beads of 4 different colors
for a total of 24 beads. Color the key on your DNA Guide.
Step 3 Grab 2 pieces of pipe cleaners and bend them in half.
Step 4
Step 5
Step 6
Step 7
Step 8
Hold one of the thin wires near the end and add a G bead and a C bead. Thread the end of the other
thin wire back through the G and C beads in the opposite direction make the wires form an X shape.
Pull the ends as if you were “tying” a knot.
Step 9 Add more big beads (SUGARS & PHOSPHATES) to the backbone – TWO on each side. Thread
the THIN wire through the large beads as you add the big beads to the THICK wire.
Step 10 Continue building the DNA molecule following the same process.
Explain to the students that DNA profiling was first used in the 1980s as the most effective
identifying evidence.
Part B: DNA Isolation?
Ask the students how do you think scientists get DNA from crime scene samples? Explain to them
that we are going to Isolate/ get DNA from a banana is a way similar to what they do in a forensic
science lab.
Step 1 - Put the rubbing alcohol in the freezer to chill for at least one hour
Step 2 - Mix about a 10% solution of dishsoap and water in the measuring cup (ie: 90 mL water + 10 mL
soap)
Step 3 - Chop the banana into about 1 inch sections into the dish.
Step 4 - Pour some soap water in (enough that you think it will cover the banana once it is mashed)
Step 5 - Add 1 tsp salt
Step 6 - Mash it with the fork until it is quite smooth
Step 7 - Fasten the coffee filter onto the cup with the elastic band. Make sure there is a pouch to
pour the fruit in, but plenty of room for the liquid in the bottom of the cup.
Step 8 - Pour the banana mash into the filter and put it in the fridge. Check on it in a few minutes
and add more fruit until it is all filtered through.
Step 9 - Pour the liquid into the small cup until it is about 1/3 full
Step 10 - Tilt the small cup and GENTLY pour cold rubbing alcohol down the side to nearly fill the cup
Step 11 - Let in sit on some ice or in the fridge for a few minutes and the DNA will precipitate in the
middle, between the banana juice and rubbing alcohol.
Step 12 - You can scoop it with toothpicks or popsicle stick or a medicine dropper
Explain to the students:
Every cell in your body has the same DNA in it! We used banana cells because they're easy to collect.
DNA is found in the nucleus of a cell, which is the "control center" for the cell. To get the DNA out,
you needed to break open the cell, detergent will burst the cell membrane (the outer layer of a cell)
and let the DNA and other cell "innards" float out. Adding the ethanol (or alcohol) separates the DNA
strands from the other stuff inside your cells. Scientists actually use a similar technique in their
laboratories to isolate DNA for further experiments, like DNA profiling.
Part C DNA and proteins.
We use four letters to code all the information contained in DNA: A, T, C and G. The letters are used
in groups of three. A group is called a codon. DNA contains the information that is needed by your
body to make proteins. The different proteins have specific functions, such as making our hearts,
hair, eyes and ears. The smallest part of proteins are amino acids. There are 20 amino acids. One or
more can make up a protein, depending on the specific protein.Each amino acid is represented by at
least one codon. Because each codon is coded with three letters, the string of letters used to
represent the amino acids in a specific protein can get pretty long. To avoid this, scientists have made
a kind of shorthand, and have given each amino acid its own letter, corresponding to our alphabet.
Using this shorthand to represent the amino acids in a protein is a way of describing, or "spelling" this
part of the protein. Written in this shorthand, the code is called the DNA Alias; each letter in the
DNA Alias actually represents a group of three letters (a codon).
When scientists see the DNA Alias of a particular protein, they can find the protein's DNA sequence
by reversing the coding process. For fun, we can perform the same process on any word by converting
each letter to the corresponding codon, and in so doing, find its "DNA sequence". Let's try it with
your name.
Write each letter of your name on the lines below:
____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____
Use the table below to help you convert your name into its DNA Alias.
Step 1: Find each letter of your name.
Step 2: Look at the Simplified Codon column to find the DNA code for each letter.
Step 3: Replace each letter of your name with its three-letter codon:
___,___,___ ___,___,___ ___,___,___ ___,___,___ ___,___,___
___,___,___ ___,___,___ ___,___,___ ___,___,___ ___,___,___
___,___,___ ___,___,___ ___,___,___ ___,___,___ ___,___,___
Step 1: Cut the elasticized cord into a 10 cm-long piece. Knot one end of the cord in order to prevent
the beads from sliding off.
Step 2: Match the first letter of your DNA Alias code to the base colour (shown in the legend above)
in order to determine the colour of the first bead. Select the first coloured bead and string it on the
cord. Repeat until all letters of the code have been represented, in the correct order, on the cord.
Remember, each letter of your name is represented by a three-letter codon, so you will end up with
three times as many beads as there are letters in your name.
Step 3: String the lanyard hook on the elasticized cord and secure it to the cord with a double knot.
Cut off any extra cord.
Compare the sequence of colours in your zipper pull with the sequences in the zipper pulls of others.
Scientists are doing the same kind of thing when they compare the different combinations of proteins
that are found in living things. Studying proteins helps us learn more about diverse topics such as
diseases and food, as well as about the diversity of life forms such as plants, animals and others.
4. Curriculum Connections
Understandings - Topic D: Evidence & Investigation
Recognize that evidence found at the scene of an activity may have unique characteristics that allow
an investigator to make inferences about the participants and the nature of the activity, and give
examples of how specific evidence may be used.
1-Investigate, with guidance, the nature of things, demonstrating an understanding of the procedures
followed.
2-Recognize pattern and order in objects and events studied; and, with guidance, record procedures
and observations, using pictures and words; and make predictions and generalizations, based on
observations.
3-Construct, with guidance, an object that achieves a given purpose, using materials that are provided
4-Demonstrate positive attitudes for the study of science and for the application of science in
responsible ways.
5-Use, safely, a variety of tools, techniques and materials in construction activities.
6-Construct structures, using a variety of materials and designs, and compare the effectiveness of
the various materials and designs for their intended purposes.
7-Evaluate the suitability of different materials and designs for their use in a building task.
Write each letter of your name on the lines below:
____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____
Use the
Step 1:
Step 2:
Step 3:
table below to help you convert your name into its DNA Alias.
Find each letter of your name.
Look at the Simplified Codon column to find the DNA code for each letter.
Replace each letter of your name with its three-letter codon:
___,___,___ ___,___,___ ___,___,___ ___,___,___ ___,___,___
___,___,___ ___,___,___ ___,___,___ ___,___,___ ___,___,___
___,___,___ ___,___,___ ___,___,___ ___,___,___ ___,___,___