Download Heredity Unit

Heredity Unit
LESSON PLAN: DAY ONE
Standards
LS.13 The student will investigate and understand that organisms reproduce and transmit
genetic information to new generations. Key concepts include…
e) characteristics that can and cannot be inherited;
g) historical contributions and significance of discoveries related to genetics.
Resources
Worksheets and materials required for this lesson are either included in the lesson plan or
attached to the end of the unit.
Topic
Genetics begins…
Instructional Objective(s)
Understand that…
- Genetic inheritance, observed through physical traits, can be explained through
Mendel’s Laws.
- Genetics and heredity is, like any scientific field, the result of key discoveries and
contributions of scientists of the past.
Know…
- The definitions of: traits, dominant traits and recessive traits.
- The key discoveries and contributions of Mendel to genetics.
Be able to…
- Evaluate the effect of the contributions of Mendel to the field of genetics.
Materials & Resources
Students would need to be provided with…
- the dial on which to calculate “genetic score” (included under “Engage”)
- 2 bags containing green and white pea plants according to the ratios described in
the “explore” section of the lesson
- half sheet of paper with question on it for exploration and for discussion (included
under “exploration”)
- formative assessment worksheet (attached to end of unit, called “What Mendel
Found…”)
Engage
As this is the first activity in the Heredity unit, the “Engage” activity would aim to
encourage an excitement in the students for the overall topic. Students would be given
the following:
And asked to, individually, calculate their “genetic score”. As a class, students would then
be asked to share the scores that they received (it would be hoped that some students
would have the same score). Students would be asked if they see similar “physical
characteristics” between students of a similar score. Students would be asked if they
remember another name for “physical characteristic” (trait) from the unit that they did on
Mendelian genetics.
Explore
Students would, in this time, be introduced to the idea of Mendelian genetics. It would be
hoped that they would gain an understanding of the findings of Mendel, being able to gain
a glimpse of what he saw. To do this, students would, in small groups, be provided with 2
small bags – one labeled “experiment 1” and one labeled “experiment 2”. The first bag
would have a picture of a green and a white pea plant on the front, separated by an
addition sign. They would be labeled as “PURE”. Inside this bag would be many real green
pea plants (about 15-20). The second bag would have no picture on the front, rather, it
would have a label with 2 blank spaces, separated by a “+” sign. This bag would also be
filled with about 15-20 plants, but they would be of both green and purple in a 3:1 ratio.
Students would be provided with the following instructions on a half-sheet of paper:
1.) Draw from bag 1 a single pea plant, record in your notebook whether the
plant is green or white (in a table). Repeat this 10-15 times.
2.) Attach two of these offspring to the blank spaces on bag 2: these are the
new parents.
3.) Draw from bag 2 a single pea plant, record whether the plant is green or
white (in the same table). Repeat this 10-15 times.
4.) Talk to one another about the results that you have found. Record, in
sentence form, about 3 observations, at least one of which should be
unexpected.
Explain
Students are asked to, as a group, discuss the observation that they included as
“unexpected”. They are to come up with a possible reason for this observation, what they
think might have happened.
Each group, then, presents to the class their “unexpected” result and the reason that they
think this occurred. (Students should in some way allude to the fact that to produce a
WHITE pea plant, two GREEN pea plants were combined… their explanation might be that
there was still some of the WHITE trait IN the offspring of the first bag, even though it
didn’t show physically).
After all groups provide their reasoning for their “unexpected” result, the terminology of
“dominant” and “recessive” would be introduced (if students have not already). These
terms would be matched with the observations of the students – i.e. if a student
expresses the idea of a “hidden” trait that shows up in a following generation, the teacher
would be able to match this with the term “recessive”. Students would also be introduced
to the idea of a “hybrid” – an organism made up of both a “dominant” and a “recessive”
gene.
Extend
To extend students, they would be asked to repeat TWICE the second part of the
experiment (bag 2) and record results in a table. Students would be asked to look for a
trend in their results, to see if there is a consistent ratio between the number of green pea
plants and white pea plants produced (may have to spend a little time discussing the word
ratio). Each group is to then record their approximate ratio and asked: “Using the
terminology discussed, what might be the reason for this difference in the proportion of
green/white pea plants produced?” (i.e. using the terms dominant and recessive).
After students have discussed this in their groups, they would be asked as a class, to
close, how they think that this discovery might have influenced science and us today. The
class would be asked to brainstorm dominant and recessive traits that we can see in
people today (e.g. brown eyes versus blue eyes, brown hair versus red hair…) and
reminded that this is a similar principle to the green pea plants vs. white pea plants that
Mendel found.
Evaluate
Students would be asked to produce a flow chart of Mendel’s experiments and results and
answer a question relating to the impact of Mendel’s findings (see worksheet at end of
unit “What Mendel found”). This would be appropriate formative assessment, completed
individually, so that the teacher has an understanding of the student’s level of
understanding.
Connections
This lesson opens up the heredity unit. It is designed to provide a foundation for students
to learn from. It is hoped that, through beginning with history, students will understand
that their learning has a place in history – it is not random, but, rather, the result of years
of work. It also sets up a foundation on which to build the ideas of genotype and
phenotype in the lesson to come.
Safety Considerations
There are no specific safety hazards that would be a concern in this lesson.
What Mendel Found…
FORMATIVE ASSESSMENT
(1) In each “bubble”, draw colored pictures of the pea plants “parents” and pea
plant “offspring” for both stages of Mendel’s experiment.
(1) Parents…
(2) offspring…
(3) Parents…
(1) Offspring…
(2) How do you think Mendel’s discoveries have impacted the field of genetics
today?