Mendel’s Peas Please
Ideal Course for Lesson to be Taught: Advanced High School Biology
Length of Lesson: 90 minutes
Authors: Amanda Maez
Lesson overview:
This lesson not only introduces students to the basics of genetics including: Inherited Traits,
Alleles, Dominant and Recessive Traits, Hybridization, Self-Pollination and Cross-Pollination,
and F1 and F2 Generations, but also gives them a historical framework from which to draw.
It is based around Gregor Mendel’s (1822-1884) original experiments on pea plants and the
numerical relationships between traits. It allows students to first examine some of their
own inherited traits, and then use historical information to discover why inheritance acts in
the way it does.
Performance objectives – students will be able to:
-Understand the basics of genetics and inheritance based on Gregor Mendel’s original
experiments with pea plants.
-Evaluate data from a hypothetical experiment with pea plants.
-Predict the outcome of certain genetic crosses.
-Explain why Gregor Mendel’s work was so foundational to the history of science.
Standards Addressed:
History Standard: The student uses a working knowledge and understanding of
significant individuals, groups, ideas,events, eras, and developments in the history of
Kansas, the United States, and the world, utilizing essential analytical and research
skills.
Benchmark 2: The student uses a working knowledge and understanding of individuals,
groups, ideas,
developments, and turning points of the Age of Revolutions (1650-1920).
Benchmark 5: The student engages in historical thinking skills.
LIFE SCIENCE – The student will develop an understanding of the cell, molecular
basis of heredity, biological evolution, interdependence of organisms, matter, energy,
and organization in living systems, and the behavior of organisms.
Benchmark 2: The student will demonstrate an understanding of chromosomes,
genes, and the molecular basis of heredity.
3. ▲ understands hereditary information is contained in genes, located in the chromosomes of each
cell.
Lesson Bibliography:
Gregory, Frederick. Natural Science in Western History. Vol. 2. Boston, MA: Houghton Mifflin,
2008. Print. Newton to the Present.
Stark, Louisa, Molly Malone, and Harmony Starr. "Inherited Human Traits: A Quick
Reference." Learn.Genetics™. Howard Hughes Medical Institue, 2008. Web. 10 Apr.
2011. <http://learn.genetics.utah.edu/>.
Materials:
-One copy of “Inherited Human Traits: A Quick Reference” for each student in the class
-PTC Taste Paper (one strip/student)
-One copy of “Learn.Genetics Worksheet” for each student
-One data sheet for each student
-One Evaluation for each student
Safety considerations:
Students should abide by all classroom safety rules. When ordering the PTC paper for testing,
make sure it is from a reliable source and contains only from .005-.007mg of PTC, as large
amount of this chemical can be toxic (As long as the substance is regulated it is not
harmful.) Make sure each student only gets one piece of PTC paper.
Note: if there is concern about including PTC in the lesson, just leave it out. There is much
research to show that it is just about as toxic as table salt if used in large amounts, but its
use is at the teacher’s discretion.
Engagement
Time: 15 minutes
What the teacher will do
Give each student a
copy of “Inherited
Human Traits: A
Quick Reference”
and a copy of “Are
you Dominant or
Recessive?”
Worksheet
Write ‘INHERITED
TRAIT’ on the board
in front of the class
What the teacher will say
Probing/eliciting questions
Specific possible student
responses
Who can tell me
what an inherited
trait is?
Skin color, eye color,
hair color, a disease,
physical characteristics
(this will be the first
of several vocabulary
words the students
will encounter today)
determined by genes
And who do we
inherit these traits
from?
Put students into
random groups of
three, and direct
their attention to the
articles.
Our parents,
grandparents, etc.
That’s right, our traits
are passed down to us
from our parents.
This article contains
Can someone tell me Dominant and
several traits that are what the two types of Recessive; widow’s
easily recognizable.
traits named in the
peak
background
information section
are?
Write ‘DOMINANT’
and ‘RECESSIVE’ on
the board
Does anyone else
recognized any other
vocabulary words in
the background
information that they
have not seen before?
Allele; genes;
observable
characteristics;
conception;
As students mention
‘ALLELE’ and ‘GENE’,
write them on the
board.
Instruct the students
to begin going
through the article
and filling out the
worksheets based on
whether they are
dominant or
recessive for each
trait. (Allow 10
minutes)
Students may struggle
with being able to
determine which allele
combinations they
could possibly be.
Walk around the
room and address
questions about allele
combinations and
other questions, but
save the discussion
about alleles with the
whole class for the
EXPLAIN.
Transition to the
history aspect and
EXPLORE portion of
the lesson.
Does anyone know
1998; ancient Greece;
when scientists first
various answers
started to think about
genes and inherited
traits?
Exploration
Time: 15 minutes
What the teacher will
do
What the teacher will say
Probing/eliciting questions
Specific possible student
responses
Introduce Gregor
Mendel’s
experiments with
pea plants and tell
the students they
will be conducting
similar studies to
Mendel’s by
observing data from
different
Before anyone knew
anything about DNA
or genes, a monk
from Austria named
‘GREGOR MENDEL’
pioneered the field of
‘GENETICS’ in the
1800s.
Does anyone have
any idea how he
might have done this
without the use of
microscopes or any
of the technology
scientists have today?
No; maybe he used
animals?; I don’t know
hybridization
crosses in pea
plants.
Can anyone think of
Bugs; plants!
something that has
observable
characteristics, but
reproduces much
faster than a human
or an animal (in other
words, many
generations can be
observed over the
course of several
years)?
Yes! Mendel studied
plants, fairly simple
plants in fact. At his
monastery, they gave
him a garden that
was 120 feet by 20
feet where he studied
about 30,000 pea
plants in eight years.
As a vocabulary
term comes up,
write it on the
board.
With the students
still in their groups
of three, hand each
student a worksheet
with “data” from
Mendel’s
experiment. On the
back of the
worksheet should
be the list of
Mendel Selected and
organized his plants
based on seven
characteristics, but
we will only use two
of those
characteristics today.
(seed color and seed
shape).
vocabulary terms
for the day.
Without knowing the
genetic code and the
specific DNA
sequence and
without being able to
see the genes
themselves, how do
you think we will be
able to determine
what is dominant and
what is recessive?
Yes, we’re going to
look at the
characteristics of the
different generations
of plants, just like
Mendel did, and
determine which
alleles they have.
Have the students
work together to
determine how
dominant and
recessive alleles act
on physical traits,
and then predict the
results of certain
crosses of alleles.
Be sure to walk
around the room
and help the
students as they are
filling out the
worksheets since
this is presumably
the first time they
will be working on
genetic crosses.
We know that traits
are determined by
the action of two
alleles. Some alleles
are dominant and
some are recessive.
Each of the traits on
the worksheet shows
1 of 2 phenotypes (or
physical trait
determined by
genetics)—Dominant
or Recessive. Try to
determine the 2
alleles of each of the
parents based on the
phenotypes of the
offspring generations.
By looking at the
characteristics of the
plants.
Have them try to
figure out the alleles
of the parental
generations on their
own first, but if they
are stuck, try to
lead them to the
correct answer.
Do you notice
anything about the
ratios of a certain
trait to another trait?
What is the best way
of organizing your
data?
Yes, the F2 Generations
all have 3:1
Dominant:Recessive
Putting it in tables,
putting it in lists…
Explanation
Time: 10 minutes
What the teacher will do
What the teacher will say
After students have
completed the
inheritance of peas
assignment, first
discuss the
vocabulary terms in
the list.
Before we discuss our
Mendel worksheets,
let’s talk about some
of the vocabulary
terms that we have
come across so far in
class today. So I
would like everyone
to take out their
Vocabulary
worksheets and we
will fill them in
together.
Probing/eliciting questions
Specific possible student
responses
Can someone
hypothesize a
definition for one of
the vocabulary words?
I think that dominant
means that most
people have that
trait…
That’s a good guess,
actually, that’s not
always the case with
traits. The fact that a
trait is dominant does
not mean it’s
common, it just
means it will win out
over recessive.
The definition of
DOMINANT is…
(use definitions from
the students’
textbooks or
definitions you plan
on using in
assessment, so that
they can refer back to
them and do not get
confused)
Go through all of the
terms on the list,
thoroughly, but
quickly in lieu of time.
(it would be a good
idea to have a list
filled out before class
to place on an
overhead, so that the
students can refer to
it as each term comes
up in discussion)
Now discuss why
they were able to
predict the outcomes
of certain crosses of
alleles.
Now let’s refer back
to our worksheet
with Mendel’s data.
Can somebody tell me
what they predicted
for a parental
generation based on
the characteristics of
Ya, for the first one,
we think that one
parent has both
dominant alleles and
the other has both
VERY GOOD! You
have just done exactly
what Mendel did! He
discovered that
phenotypes were not
the offspring
generations?
recessive.
What do you think
about the second
cross?
We think this parent
has one dominant
and one recessive
allele and this parent
has two dominant
alleles
Ok great, can you tell
me how you came to
that conclusion?
Well, we thought
that both of the
parents were both
dominant for both
alleles at first because
both parents have
the dominant trait,
but then when you
look at the F1 and F2
generations, there
are recessive traits
present too, so we
figured that one of
the parents has to
have on recessive
allele.
always what were
expected, and he was
able to explain why
that happened, and he
came up with a law
about crossing
different traits that we
still use today.
Discuss how Mendel’s
work was
foundational in the
area of genetics and
how the numerical
relationships between
traits that he
discovered allowed
him to predict certain
outcomes even
though he didn’t
actually know all the
was contained within
a gene.
Mendel was one of
the founding fathers
of genetics, and he
was able to do
something that has
lasted for decades.
Why do you think his
work was so
foundational?
I don’t know, he just
grew plants….
Well did Mendel know
that traits were passed No
on by genes?
Did he know that each
trait was determined
No; Maybe; I don’t
by two alleles?
know
Did he has a
microscope to look at
the DNA of his plants?
You’re right. Mendel
didn’t have any of the
technology that we
have today. He made
hypotheses based on
what he observed in
nature.
Correct! Mendel
made a prediction
that was able to be
Can anyone tell me
why Mendel’s
hypothesis was a good
one?
No
It was testable and
observable.
tested and
reproduced. The
other thing about
Mendel’s experiment
was that he gathered
a lot of data! The
more data you gather,
the more convincing
your conclusions will
be.
Mendel is a very
important scientist
because he laid the
foundations for the
study of genetics, and
the work he did is still
used today!
Elaboration
Time: 7-9 minutes
What the teacher will do
What the teacher
will say
Probing/eliciting
questions
Specific possible
student responses
Have the students separate into
groups of two and work at a
computer in pairs. If students
finish early with the EXPLORE,
they can begin working on this
portion of the lesson while
other groups finish up.
Direct the students to
http://learn.genetics.utah.edu/
As they tour the interactive
website, have them fill out a
“Learn.Genetics” worksheet
As you explore
this website, be
sure to take
notes, and think
about what you
Students will
comply.
have learned
about genes and
genetics and how
that can be
applied to some
of the things on
this website.
Evaluation
Time: 8 minutes
What the teacher will do
What the teacher will
say
Probing/eliciting questions
Hand out an
evaluation to each of
the students and
answer questions
they may have about
the wording of a
question.
Specific possible student
responses
Students will work on
their evaluations until
the class period is
over.
Name:_________________
Mendel’s Peas Please—Evaluation
Please select 3 of the 11 vocabulary words to define in your own words.
Inherited Trait
Allele
Gregor Mendel
Genetics
Dominant
Hybridization
Self-Pollination
Cross-Pollination
Recessive
F1 Generation
F2 Generation
1.
2.
3.
When and where did Gregor Mendel study pea plants?
a. 1860s in New Zealand
b. 1980s in France
c. 1860s in Austria
d. 1900 in Germany
What are some important aspects of Mendel’s original experiment that made it so
successful?
a. Used a large variety of species.
b. Selected varieties that differed in but one or a few characteristics, so that he could
isolate the effect on the traits in the offspring.
c. Summarized the relations by comparing how many showed which traits (tried to
show a numerical ratio).
d. Preformed experiments on only one generation.
e. A, B and C
f. B and C only
g. all of the above
Why was Gregor Mendel’s work with pea plants so important in the history of science?
Name:______________________
Trait
Example
Earlobe attachment
Tongue Rolling
Cleft Chin
Dimples
Handedness
Freckles
Naturally Curly Hair
Hand Clasping
Color Blindness
Hairline Shape
PTC tasting
Dominant
X
Recessive
Possible Allele
Combination(s)
Aa, AA
What alleles do you think your parents have? Your grandparents? Why?
Can you think of other traits you may have gotten from your parents?
Term
Inherited Trait
Dominant
Recessive
Inheritance
Allele
Gregor Mendel
Genetics
Hybridization
Self-Pollination
Cross-Pollination
F1 Generation
F2 Generation
Definition
Name:_______________________
Instructions:
1. Go to http://learn.genetics.utah.edu/.
2. Feel free to look around and click on some areas that interest you about genetics
(Basics, DNA, cells, technology, virtual labs)
3. Tell me about what you learned:
Which area did you spend the most time learning about?
____________________________________________________________________
Please list a few new vocabulary words you learned and their definitions (if you are
unsure of their definitions, look them up in your textbook or online):
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
What was the most interesting thing you learned about genetics from this website?
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
How can you apply what we learned today about genetics to what you learned on the
website? (“I cannot apply anything” is NOT a sufficient answer.)
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
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