Course Structure
Students
Course Content
My Work
- Lab Work
- Sample Lesson: Farmer Funk's Funky Dihybrid
Corn
Students take general biology in tenth or eleventh grade at Friends Select. The course meets four times a week for three 40-minute periods and one 80-minute period. The 40-minute periods are usually used for lecture, demonstration or assessments, such as quizzes and tests. The 80-minute period is usually used for labs, although there was some flexibility in this schedule.
Each of the three classes I worked with had 14-16 students. The desks were arranged in rows in front of a board at the front of the room, and there were lab benches and additional work space at the back of the room. For lab, there was a wide variety of equipment, resources and materials available.
Students were assesssed in a number of different ways throughout the course:
- homework
- tests and quizzes (multiple choice and short answer)
- group and independent projects (i.e. making a 3-D DNA molecule structure)
- weekly lab reports
There was a wide range of student ability and interest in the general biology classes that I worked with at Friends Select. Most students were accustomed to a traditional lecture format, and I often found it difficult to engage them in more interactive activities. Some students were able to think critically and abstractly with relative ease, whereas others often struggled with memorizing and understanding basic concepts and terminology. Some students came in regularly for help outside of classes, but most did not.
The dynamics in the three classes were very different. One class was very quiet, almost never asking questions, but worked well when doing independent and small group work. Another class was very dynamic during lecture, asking a lot of questions. However, many students had difficultly focusing and staying on task during lab.
The following are the major topics and concepts that were taught during the three months I was student teaching at Friends Select Upper School:
- DNA
- Molecular Strucure
- Replication
- Function and Protein Synthesis
- Genetics
- Mendelian Inheritance
- Indpendent Assortment
- Monohybrid and Dihybrid Crosses (Punnett Squares)
- Codominance
- Incomplete Dominance
- Genetic Engineering
- Mendelian Inheritance
- Plants
- Basic Anatomy and Physiology (Roots, Stems and Leaves)
- Evolution
- Reproduction (Flowers, Seeds and Fruits)
After two weeks of observing the classes, I assumed the responsibility of designing and teaching the labs for all three general biology classes for the remaining eight weeks that I was student teaching in the upper school. I spent 15-20 minutes introducing the lab and left the rest of the 80-minute period for students to work independently. Most of the labs were designed to be self-contained within the 80-minutes period, however, I developed one long-term lab that continued over a three-month period.
- DNA and Chromosomes: Observing barr bodies and Creating karyotypes
- Mendelian Genetics:
- Comparing the predicted and actual occurances of human monohybrid traits
- Investigating the origin of dihybrid corn
- Genetics, Evolution and Plants - Long-term lab: Testing for differences in success between different phenotypes of Arabidopsis under environmental stress
- Plant Anatomy and Physiology: Observing plant root, steam and leaf tissue
- Plant Evolution and Reproduction: Observing plant flowers, fruits and seeds
Sample Lesson:
Mendelian Genetics
Farmer Funk's Funky Dihybrid Corn:
Investigating the Origins of Dihyrid Corn
- I wanted to design a lab that reinforced the concepts and procedures (especially the Punnett Square) that the students had learned in class while requiring them to apply these concepts and procedures to a new scenario.
- All students will successfully use Punnett Squares
to outline the dihybrid P and F1 generation crosses that occurred to
produce a phenotypically mixed F2 generation corn cob sample.
- All students will successfully use Punnett Squares to demonstrate the selective process that must occur to breed pure corn cobs from a pheontypically mixed corn cob sample.
Day 1 (80 minute. Lab)
1. Group Introduction (20 min.)
- Tell the students that we are going to talk about corn
sex!
- Ask students to summarize how a corn plant reproduces – illustrate reproductive cycle on the board.
- Make sure that all students understand that each corn
kernel on a cob has its own genotype. A whole cob includes all the individuals
in a generation produced by one cross.
The Problem
Lab Instructions and Guidelines click here
- Tell the students that they are going to be asked to
solve a problem involving plant sex and genetics.
- Hand out the lab instruction sheet and ask the students
to read the background information about Farmer Funk and his dihybrid
corn on the first page. While they are reading, show the students samples
of the pure purple/starchy, yellow/starchy, purple/sweet and yellow/sweet
corn cobs.
- Ask the students to brainstorm what they think the
mystery will be (cross-bed corn).
- Ask what the cross-bred dihybrid corn will look like.
Show them four samples (1:1:1:1, 9:3:3:1. 3:1 and 1:1 ratios) of the
phenotypically mixed corn cobs.
Strategies
- Ask the students to read the second page of the handout
that describes the problem and what information they need to discover.
- Afterwards, ask the students to share strategies for how they could solve the problem.
- There are a couple possibilities here, but students
will probably decide that the best method will be to first calculate
a ratio for the kernel phenotypes that are on the cob. Using this ratio,
they can then think of the types crosses they have learned in class
that produce the same ratios. This same method will allow them to trace
back one further generation to identify the possible parent genotypes
from the original crosses between pure strains.
- Do a sample backward-cross diagram on the board and
show students the format in the handout that you would like them to
use to organize their results.
2. Lab Part I: Identifying the F1 and Parent Crosses (60 min.)
- Divide the students into four groups and give each
group a mixed corn cob sample. (Give students who already have a firm
grasp on the concepts and procedures corn with a 1:1:1:1 or 9:3:3:1
ratio instead of a 1:1 or 3:1).
- Explain that they will work together to identify the F1 and parent crosses that occurred to produce their mixed corn cob sample.
- Ask the students to make a backward-cross diagram using
large paper and crayons, which they will use to present their findings
to the rest of the class.
- Allow the students to work in their groups, helping
them as needed.
- After 30 minutes of work, ask each group to make a
5-minute presentation to the rest of the class, using their diagram
to explain what they did to identify the crosses that occurred (Ask
that everyone in the group explain some aspect of the process).
- For homework, ask students to read Part II: How to return to the purebred lines and the Lab Report guidelines in the handout.
Day 2 (40 minute class)
1. Group Introduction (10 min.)
- In order to give students plenty of time to work together
in their groups, ask someone to briefly summarize what they need to
do to complete Part II of the lab.
- If necessary, demonstrate a sample set of crosses on
the board that will select for the purebred corn cobs.
- Before breaking into groups, briefly go over the Lab
Report guidelines on the last page of the handout to make sure that
students are clear as to what is expected of them. Make it clear that
each student must hand in his/her own, unique lab report which includes
his/her own version of the results and conclusions.
2. Lab Part II: How to Return to the Purebred Lines? (30 min.)
- Have students break up back into their groups from
the last class. Give them their same mixed corn cob sample and ask them
to create a diagram that visually demonstrates the selective process
that they would use to return the corn stock to its purebred status
using the kernels from their mixed sample. They should include the number
of generations it will take to get purebred corn from different phenotypes
and show what percentage of the crop will need to be selected out or
continue to be self-bred.
- As long as students follow the general guidelines in the handout and are clear about showing their work and thought process here, there is no one right answer. I purposefully left this part of the lab open to the students’ subjective interpretation by asking them to make economic- and time-conscience decisions. This part of the lab also stresses that genetics concepts have practical, predictive purposes when making decisions and are not isolated to being used for demonstration.
All students will be required to write a formal lab report that explains:
- Objective/Purpose
- Procedure
- Results/Data
- Penotypic ratio of corn kernels on the cob
- Diagram of the crosses that occurred to produce
the mixed dihybrid corn (generations P,F1 and F2)
- Penotypic ratio of corn kernels on the cob
- Observations
- Conclusions
- Written explanation of how to return the corn crop
to purebred.
- Diagram of the crosses need to return the corn
crop to purebred.
- Drawn plan of how to avoid crossing between different pure strains of corn in the future.
- Written explanation of how to return the corn crop
to purebred.