Download To-Do before your first classroom visit:

To-Do before your first classroom visit:
-Look over presentation and edit it as you see fit. If you have a very short class period, you may want to
select only certain model organisms to focus on in the latter half of the presentation. Definitely leave
time for students to ask you questions about yourself – this is the most valuable part of your visit!
-Decide if you have time to carry out both activities and choose based on your interest level. The
number line part is worked into the presentation so it might be easier to keep this part, but presentation
can be edited to only do the disease research part if you find this more interesting!
If you will be doing the Disease Research Activities:
1.Pick one disease per ambassador (two if there are only one or two ambassadors) and make sure you
have the Ambassador Disease Description slides and model organism example slides that correspond
with these diseases. Examples are color-coded by disease so you can easily check if students are on the
right track.
2. Separate model organism examples by model organism symbol. The examples sorted by model
organism are what you will give to each student “model organism lab” during the second activity.
Model Organism Module – DNA Ambassador Presentation and Activity Guide
What is DNA Day?
-DNA Day commemorates two major events in the history of our understanding about DNA.
-In April 1953, James Watson and Francis Crick determined the structure of DNA.
-50 years later, in April 2003, the Human Genome Project determined the entire sequence of human
DNA. Research scientists are using the knowledge and technology generated by this project to further
understand how your DNA sequence can contribute to disease.
What is a genome? A genome is an entire set of an organism’s DNA.
You’re probably familiar with seeing a set of chromosomes, which is how an organism’s genome is
condensed and packaged.
The human genome contains 23 pairs of chromosomes, i.e. 46 total.
You have pairs of chromosomes because you inherit one from your mother and one from your father. In
total, 23 chromosomes from each parent.
Does every organism have 46 chromosomes? No, some have many more, and some have just one (like
bacteria, viruses).
Every cell in your body contains a copy of your genome. That means every cell in your body has a full set
of chromosomes.
That’s a lot of DNA. All the DNA in your body sums up to about half a pound.
DNA holds instructions for the cell
DNA is a long molecule composed of a combination of 4 nucleotides.
DNA encodes instructions for the work a cell should be doing.
It’s like a language for your cells, except the alphabet it uses only has 4 letters.
The nucleotides are the four small molecules adenine, thymine, cytosine and guanine, abbreviated by A,
T, C and G.
The DNA in your cells is actually composed of two molecules of DNA held together by nucleotides
pairing with each other.
The two molecules are said to be complementary. The shape that they form when paired is a double
helix
DNA sequence is the order of nucleotides on a DNA molecule
When we look at a double helix, we only need the sequence of one of the molecules. Why is this?
Since nucleotide pairing follows strict rules, we can always figure out the sequence of the
complementary DNA molecule.
If we unwind one of the molecules and write out its nucleotides in order, this is its DNA sequence.
Some sections of the genome are genes.
A gene is a segment of DNA that contains instructions for the cell to make a protein.
A protein is a large molecule that does a specific task in the cell, like breaking down cell waste or
importing nutrients.
The human genome contains about 20,000 genes.
One way to think about the role of the genome is like it’s a cookbook for the cell.
The nucleotides are like letters, arranged in certain ways to make words.
Genes are like entire recipes for the cell to make.
Having only four different types of nucleotides doesn’t seem like it would give you much variety, but
think of how much the order matters in the letters in a book.
If you kept all the same letters in a book, but scrambled them, would you have the same book at all?
The entire human genome comprises over 3 billion base pairs. Here’s just the beginning.
This is the sequence of the very beginning of chromosome 1. This is showing the first 954 nucleotides.
If you tried to put the entire human sequence into a power point presentation, it would take about 6.3
million slides! ...And be a very boring presentation.
Variations in the DNA
Variations in the sequence of these letters can cause variation in phenotype – both positive and
negative.
How can we study?
Why might it not make sense to always experiment on humans?
Pause to ask people for reasons why it might not be feasible to experiment on humans
Luckily, we have…
-In the past few decades, genome sequencing has become cheaper
-So, we have sequenced the genomes of many animals, so now there are lots of animals that have full
sets of genomic resources
Some of these are model organisms
Note that besides genome, true model organisms often other aspects (laboratory and otherwise) that
contribute to their usefulness.
Generally have a clear way in which they relate back to humans
What allows us to use model organisms?
All organisms come from the same ancestor
Expected to share many aspects of their biology
How much they share will depend on how closely related they are to humans – i.e. Drosophila can’t be
used to study bone development but can be useful in many other ways.
Hox genes
Hox gene clusters are one example of the above principle
Since we know animals share this – we can manipulate the gene in other organisms without harming
any actual humans
Phylogenetic tree – see notes on slide
Activity 1, instructions for the student:
• You will be working on a short exercise with the students sitting closest to you
• Your group will receive laminated sheets number lines with the following traits on them:
•
- Length of life span
•
- Number of offspring in lifetime
•
- Percent of genes shared with humans
• You will also receive markers representing each of the three animals below
• For each trait, for each organism (fly, mouse and worm), your group will mark your estimates of
each trait.
•
Afterwards, you will learn how close your guesses were.
Notes for Ambassador:
While one person introduces activity, have others hand out materials.
We will send you enough so that every 2-3 students has their own laminated sheet
Give each group a three fly decal, three worm decals and a mouse decal to stick to their laminated
sheets.
Give them 5-10 minutes to do the activity.
Slides 21-31:
Each slide will reveal one more answer
Before revealing each answer ask for student volunteers to guess their answers
At the end of each category, ask students why that category is important (i.e. why we might want want
short life spans etc.)
Slide 32:
After revealing last answer, point out that life span and # of offspring correlate negatively with
relatedness to humans – so there need to be tradeoffs. Mice allow you to study vertebrate systems
more directly, but do not have some of the other advantages of the other model organisms.
Model organism examples:
Ambassdor notes: Emphasize that these are just SOME of the model organisms Unless otherwise noted,
the slides will provide enough information without extensive notes needed. Please feel free to add your
own additional notes if you study one of these organisms, or to adjust the length of any of these
sections based on your interests or time.
34: Mighty microbes
First, we will consider microbes. Even though they don’t look anything like a human, they have
important uses related to human health.
35-36 E. coli and S. cerevisiae
•
Why is it studied?
• Grows quickly, the genome is easy to study and manipulate
• Unlike bacteria, yeast are eukaryotic so they have the same organelles as human cells
• Used to study aging and DNA repair
•
•
Ambassador, here would be a good place to mention some of the below facts that did
not fit:
E. coli can be manipulated to produce large amounts of proteins and enzymes for study,
and clone genes of interest (i.e. insulin for diabetes).
• Initially, the insulin given to diabetics was produced by E. coli containing the
necessary human genes.
• Scientists are designing bacteria that can be used to clean-up oil and other
38: C. elgans
-The cover of Science magazine commemorate a landmark of biology: a complete DNA sequence of C.
elegans.
- The genome is approximately 97 millions base pairs of DNA, 1/3 the size of human genome and 8 times
of the yeast Saccharomyces cerevisiae.
-Two sexes: hermaphrodite and males – can asexually reproduce to produce many genetically identical
individuals for experimentation.
-Slide 39 is fine as is unless you want to add any other details
40: D. melanogaster: still outside of the vertebrates! Drosophila is an insect.
41: Introduction to D. melanogaster
-commonly known the fruit or vinegar fly.
- It is a small insect you usually find flying around your banana or apple especially during the summer.
-Drosophila was first studied as a model organism by a famous scientist named “ Thomas Morgan” when
he was looking at bunch of flies and noticed among thousands of red-eyed flies there is a fly that has
white color eyes instead. T
-his was really interesting and weird to him, so Tom wanted to explore more about this phenotype
difference between these two flies.
-After many experiments, he concluded that the fly with the white eye has a mutation in a gene that
encodes the eye pigment color and this gene can be inherited from parents to children under the
concept of genetic inheritance
42: Advantages of D. melanogaster
-flies share approximately ~76% of their genome with
-flies’ embryos undergo similar developmental processes to form a whole organism as in humans.
- Scientists have developed a number of genetics tools such as switching gene on or off at specific time
and location. This technique is crucial for scientists to investigate the exact role of a protein/gene in a
given disease.
-In comparison to us, flies only have 4 pair of chromosomes and the fourth one is so small and only has
few genes.
-Drosophila life span is from one week to month depends on the food, temperature and genotype of
that fly. A single female fly can lay 500 eggs in a few day which means it can lay thousands of eggs
throughout her life time.
43. Danio rerio is a vertebrate – so shares even more of the same characteristics with humans than
any of the organisms we have talked about so far.
44. Fine as is, add more details as you see fit.
45. Advantages and applications of zebrafish
-You might want to mention: Just this year zebrafish have been utilized to track the single cell origin of
melanoma, and hopefully this will expand to other cancers. By discovering how the very first cell
transforms into a cancer cell, zebrafish can one day be used as a great tool in promoting cancer
prevention!
-Might want to note that with vertebrates (i.e. mice and zebrafish), you need to get special permissions
to work on them.
46. The mouse is a mammal – shares most genes and biological processes with humans!
47-48: Might want to re-emphasize that although they have more offspring and shorter lifespans than
humans, they produce fewer offspring etc. than the other model organisms we have studied today. BUT
they are much more closely related – re-emphasize trade-off.
49-50:
And finally, we have a plant model organism.
Since it is a plant, you wouldn’t think that it could provide useful information to humans – cannot be
used to directly study human disease but it can be used for agriculturally relevant traits crucial to the
organisms we study.
• -For example, the gene responsible for allowing Arabidopsis to recognize/defend itself against
bacterial flagella is well characterized. This is important because food crops like corn, soy, and
tomato are often susceptible to infection by viruses, bacteria, and fungi.
51: Now we are pausing for our second activity
52: Disease Lab Collaboration Scenario
• Different science laboratories are performing a wide variety of studies and looking to persuade
donors to give money to their labs to study different diseases!
• DNA Day Ambassadors (wealthy donors) will have a laminated card describing a disease
phenotype they are interested in studying
• Number of DNA ambassadors = number of disease cards. Up to 5 disease phenotypes
• Students will divide into several (5-8) “ Model Organism lab groups” and be given cards
describing several studies and facts involving a particular model organism
• Give each student group a printed packet of disease descriptions. Ambassadors will keep the
laminated disease cards with pictures. IMPORTANT: If you are not going to be using all 5
diseases, tell students which ones you are picking and to ignore the rest.
• Students must read the cards and find studies that relate to the diseases described by DNA
ambassadors
-Think about: Which studies and/or model organisms are relevant to the disease phenotypes? Why
should the donors give your lab money?
-They will then pass the relevant example cards back to Ambassador representing that particular
disease.
-As students are working, DNA Day ambassadors will be coming around to check on their work – once a
group has managed to correctly pass off all of their cards to the right Ambassador, they are considered
fully funded!
More details:
-Pretend scenario to make activity competitive.
-Number of DNA ambassadors = number of disease cards. Up to 5 disease phenotypes
Ambassadors will go around to groups and guide them to find studies that relate to their phenotypes
Have students give the ambassador their most relevant cards. Students should spend time debating
which examples are most relevant to which disease.
Use these studies to answer the questions on the worksheet, which fact is the most interesting/relevant,
which organism would work best
Have students present why a model organism/study is most relevant. No right answer as long as you
have a good argument!
53. Take a second to ask students what they thought was most interesting about the previous activities.
Conclusions should be fine on their own, but feel free to reiterate any other aspects about model
organisms that you find relevant or students seem to find interesting.
54: If all goes as planned, you should have time for each ambassador to further introduce themselves
and talk about their research, particularly if it relates to model organisms! Students always seem to have
lots of questions about being a professional scientist.