Lab Section 17
Rapa Fast Plant Inheritances Between F1 and F2 Generation
Lab Partner: Sam Foster
This semester, our class conducted an experiment where we examined
the inheritance of phenotypes from the plant, Brassica Rapa. Within our
experiment, we only planted heterozygous seeds, observing both the parent and
offspring phenotypes. In order to develop a hypothesis, we used the Mendelian
model to see the pattern of inheritance within the plant. Our group came to the
conclusion that the purple pigment was the dominant trait and followed the
Mendel Laws. In the end, our data outcome was inconclusive due to having multiple
type of errors which played an important role within this experiment.
According to The Monk in The Garden, the father of genetic science
was a monk name Gregor Mendel. Mendel conducted experiments within his own
garden and had discovered the main idea of heredity. According to Experimental
Inquiries, Mendel had what the book called nine lives. These nine lives
reflected on his disbelief on the evolution and how his work has been interpreted
through another scientist. Through the lens of Mendel eyes, he has discovered
many new ideas, known today as the Mendelian Laws. One law he discovered is the
Law of Segregation, where the dominant and recessive phenotypes are pass down
from the parents to their offspring. Another law Mendel discovered is the Law of
Independent Assortment, where other types of phenotypes are passed down
naturally from the parents to their offspring. Mendel’s laws display a pattern
of inheritance from the parents to their offspring where they have different
potential results. Overall, Mendel’s laws play a crucial role within this
This semester our biology class, we wanted to test whether or not
Mendelian Genetic could be proven true. The scientific question we used for
this experiment was does the purple stem phenotype pattern follow Mendelian
Laws. We hypothesized that the purple pigment phenotype was indeed the dominant
trait and did followed Mendel Laws pattern. The class predicted if the purple
pigment (anthocyanin) was the dominate trait then the F2 generation would follow
the predicted phenotypic ratio of 3:1.
The class used fast plants which contained
strips of Brassica Rapa in order to do the experiment successfully within a
semester. According to Springer Link, these Brassica has rapid seed maturation,
absence of seed dormancy and high female fertility. These fast plants are known
to have a quick breeding cycle allowing them to be an ideal plant to experiment
on. Within the experiment, the class examined the phenotypes on whether there
was a presence or absence of purple stems (anthocyanin). Leading it to be
either green or purple plants.
Before starting the experiment, these following materials were
needed in order to execute the experiment successfully. According to the lab
manual, we needed a seed-collecting pan, small envelopes, wicks, labeling tape,
styrofoam quads used to germinate seeds, a fluorescent light bank, water
reservoir for petri dish, bee-sticks, water droppers, potting mix, fertilizer,
a watering tray, and petri dishes with filter paper. Within our experiment we
deviated some of the needed materials, as well as the time line due to class
limitations such as time and materials.
1. Checklist for Brassica Rapa Fast Plant
Inheritances Between F1 and F2 Generation Experiment. These are the deviated
dates and day each of these activities are done within this experiment. These
activities are crucial to follow in order to replicate experiment.
F1 hybrid seeds. See planting seeds. Regularly check water.
seedlings and record numbers of each phenotypes. Thin plants to one per cell.
at least 6-8 flowers.
buds and shoots. Restrict water once remove.
F2 seeds and germinate in trays.
and record numbers of each phenotype
Once the materials were
gathered from the biology laboratory teaching assistant, the experiment can
begin. On day one, we filled the six-pack plant tray halfway with potting mix.
The six-pack plant tray is a deviation from the lab manual in replacement of
the wicks. Then we added two fertilizer pellets in each of the six squares.
Next, we added roughly an inch of extra potting soil on top and used our
pointer finger to depress them into the soil. Once the soil had been depressed,
we placed two seed in opposite corners of the squares and covered the seeds
with soil. We then repeated this step for the rest of the squares. After, all
12 seeds had been planted, our group sprinkled water from the sink onto the top
of each square and labeled the side of the six-pack with our name, the date and
the type of plant we planted. Here was another deviation, we used our hands to
sprinkle the water instead of having a water dropper. Then, placed the plant
into the watering tray to be placed under the fluorescent light bank. Remember
to hang the fluorescent light bank only 2-3 inch above the plant and keep the
lights on 24 hours a day.
On day 14 through 35, we recorded any observations about the plant
phenotypes. Something to note, there was a scheduling deviation from the book
due to class timing as this was supposed to be day four. On day 42, we started
to cross pollinate the bloomed flowers by using a small brush to stroke the
pollen onto another flower. The small brush was used instead of a bee stick
which is another deviation from the lab manual. Seven days later, we removed
the buds and restricted the plant to have 16 days with no water under the
fluorescent light. On day 63, we started to harvest F2 generation
seeds in trays with wet paper towel instead of petri dishes with filter paper.
We then collected the seeds, we did not use seed-collecting pans or small
envelopes. Instead, we collected the seeds and separated them into a green seed
pile and a brown seed pile on the table. Once planted into the tray it was
placed back under the fluorescent light. On day 70, we plucked out the F2
generation to examined the heterozygous markers in order to provide evidences
to conclude our results. To determine whether it passed as a purple stem, it
had to have a sheen streak of purple heading down to the roots. If it had a
dark ring around the top, it didn’t count as a purple stem. Once counted, it
was recorded onto table 2.
2. Data for total of F2 Generation
Planted and Germinated. Each section planted many fast plants containing strips
of Brassica Rapa. After harvesting the F1 generation, each section counting
their seeds in order to find the total for the F2 generation. These counts help
aid the groups hypothesis whether these plants inherited the purple stem by
following the Mendelian Laws.
# of seeds planted
Purple stem plants
Green stem plants
3. Data for Section 17 Chi Square
Results and Equations. These results will aid in discovering whether there is a
different in the theoretical and experimental data. Using this test, allows us
to determine either the hypothesis could be refuted or supported.
Green Stem Plants
Deviation (o-e) or d
Chi Square Equation: X2=å (d2/e) = 57.90
4. Data for All the Sections Chi Square Results
and Equations. These results will aid us in determining on whether these theoretical
and experimental differences support the inheritance pattern of the Mendelian
Purple Stem Plants
Green Stem Plants
Deviation (o-e) or d
Chi Square Equation: X2=å (d2/e) = 1,185.62
In conclusion, the results were inconclusive due to trial
and error. These results did not support nor refute our hypothesis, which
states that the purple stem phenotype pattern follows the Mendelian Laws.
According to table 2, section 18 has 147 purple stems and 229 green stems.
Section 18 as well as 3 other sections had green stems as the dominant
phenotype. The rest of the 21-section had the ratio to where the purple was
dominant. As we can see, section 18 refute our hypothesis due to having the
green stem phenotype being dominant. While the other 21 section supports our
hypothesis in having the purple stem phenotype being dominant. Overall, our
data both support and refute our hypothesis leading to our conclusion where the
results were inconclusive due to trial and error.
One factor of trial and error could be the time line
during this experiment. We had to deviate from the lab manual causing the
experiment to go on further than 42 days. Due to this timeline, we were not
able to confirm whether F1 generation was truly all heterozygous seeds.
Leading to another factor where we didn’t allow the F2 generation to
fully germinate to see whether these plants had the heterozygous mark because
not all of the seeds had grown yet. If were to let all the seeds germinate,
there could be a possibility that those four sections with green stem as their
dominant could be purple stem dominate because not all the seeds germinated. Also,
another factor could be a counting issue on day 70. Although, our class decided
to call purple stem by having a sheen strike of purple heading down to the
roots. Since it was done by multiple different person, each person could have
their own definition of how dark or light the sheen could be. Due to this
error, this result could have gone into a complete different direction. Another
factor that could complete change our end result is whether or not the seeds we
plant are in fact heterozygous. If these seeds were not what they claim to be
then our outlook within the experiment would have change. In the end, our data
had support and refute our hypothesis, making our results to be inconclusive.
In the future, there are many ways
to improve this experiment. One way to improve is to follow the timeline as
close to the lab manual as possible. This way, future scientist could witness
on whether the F1 generation seeds were truly heterozygous. Another
way to improve this experiment is to allow the F2 generation to
fully germinate to be able to determine the ratio as accurately as possible. If
future biology lab class were able to limit these errors than the result could
have been clearer.
Inquires. Google Books. accessed 2017 Dec 3.
Morgan JG, Brown Carter ME. Investigating
Biology Laboratory Manual. 6th Edition. San Francisco, California: Benjamin
Cummings; 2008. Mendelian Genetics: Fast Plants; p 3-15
Musgrave ME. Realizing the Potential of
Rapid-Cycling Brassica as a Model System for Use in Plant Biology Research. SpringerLink.
accessed 2017 Dec 3.
Monk in the Garden. Google Books. accessed 2017 Dec 3.