Learning from the Fossil Record
Grade 8 Science
Name: Caroline B.
Date: 1/19/11
Plant Genetics and Variation Investigation
PART 1: Setting Up the Investigation
Your group will germinate four plates of seeds and study the inheritance of plant color.
1. Plate 1 will contain 10 female parent seeds (P1) that contain two genes for the same plant color.
2. Plate 2 will contain 10 male parent seeds (P2) that contain two genes for the same plant color.
3. Plate 3 will contain seeds of the offspring of the parents above. (F1) Think of the pollen from P2
combining with the egg of P1 to create them.
4. Plate 4 will contain seeds of the offspring of two plants from F1 mating. (F2) Think of the pollen from
one F1 plant combining with the egg of one F2 plant to create them.
Follow the procedures below to set up the plates. Read and follow the procedures very carefully.
1. Use a ruler to draw a line 2 cm from the edge of a sheet of filter paper as shown below.
2. Write the date, your group’s class , your group’s table number, and the seed type on the paper as
shown below.
1/5/11 8Black- 2 P1
2 cm
3. Place the filter paper circle inside the lid of a petri dish.
4. Use a pipette to add water to the filter paper until it is completely saturated.
5. Drain off any excess water.
6. Place the appropriate seeds on the filter paper, somewhere above the 2-cm line.
7. When you have finished place the bottom of the dish on the lid to serve as a cover.
8. Place your group’s plates into a cup as shown on the diagram on the board- at a steep angle, with the
2-cm marked section at the bottom.
9. Pour water into the cup to a depth of about 2 cm. The water level should not reach any of the seeds
on the filter paper. If it does, remove the plate and reposition the seeds.
10. Leave the cups with their plates in the light box in the back of the room.
Over the next few days the seeds will germinate so you can observe and analyze their color.
Learning from the Fossil Record
Grade 8 Science
Name: Caroline B.
Date: 1/19/11
PART 2: Making and Analyzing Observations
1.
Record your observations below.
Mother (P1)
# 10 Green
Father (P2)
#0 Purple
46
# 0 Green
0
# 10 Purple
48
0
Offspring (F1)
# 0 Green
# 9 Purple
0
45
Offspring (F2)
# 3 Green
# 9 Purple
25
51
Question: How can the mother (P1) and father (P2) have an offspring when they are in different
containers?
2.
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Use the “I see…this means…” strategy to explain each observation you made.
Purple is stronger than green.
All the F1s must have a big P.
All the P2s must have a big P.
P=Purple/p=Green
The F2s must have a pp, to be green for the green children. This is certain because once
we get a big P the child is purple.
P1 must have two little p’s, because if you put a big P in the combination then the child
wouldn’t be green it would be purple.
P2 and F2 for the purple is Pp or PP. But the most likely.
Learning from the Fossil Record
Grade 8 Science
Name: Caroline B.
Date: 1/19/11
Vocabulary
Word
Dominant
Definition
Stronger Gene.
Represented by a capital letter. (Usually want to
keep it the same: P)
Recessive
Weaker Gene.
Represented by a lower case letter. (p)
Genotypes
The letters that represent the trait.
Phenotypes
The actual traits. (Physical Traits)
Homozygous Recessive (Homo means
same)(zygous means gene)
pp= two recessive genes.
Homozygous Dominant
PP= two dominant genes.
Heterozygous
Pp= two different genes. One dominant and one
recessive.
“Mendelian” Genetics
The study of how and why we get traits.
Is the “How”
Heredity
That we get traits from our parents through
reproduction.
Is the “What Happened”
Gregor Mendel
This is the person who figured out genetics. He
was Austrian and a monk. He was abandoned as a
child, and was raised in a monastery. He was the
monastery’s main gardener. In year one all the pea
plants had white flowers, and the next they were
two different colors. He then started to experiment
about it, and then realized “all the vocabulary
words.”
Learning from the Fossil Record
Grade 8 Science
Name: Caroline B.
Date: 1/19/11
PART 3: Drawing Conclusions/ Incorporating Vocabulary and Concepts
a.
b.
All statements in the conclusion must be supported by observations/analysis from Part 2
and/or information you learned from previous lessons.
Add and highlight any vocabulary and concepts we discuss.
When we had first started this experiment we had four different containers that were all
labeled differently. The containers were P1, P2, F1, and F2. The experiment was conducted, because we
wanted to figure out what the traits are and how they come out that way. After a couple of days we
went back to the petri dishes and wrote down data to how many purple or green phenotypes there
were in the P1 dish. Then we went to the other four dishes to also check how many purple and green
plants there were. After checking the plants, we went back and discussed all the data together and
accumulated the information to get one big number for each section. Then we had taken the data and
tried to figure out what the possible trait combinations were for each set of data. When we looked at
our data we realized that the genotypes for P1 had to be two recessive genes. We figured this out
because the purple genes were dominant and the green genes were recessive, this meant that if the P1
had at least one of the dominant genes it wouldn’t have possibly been green. The P2 was harder to
figure out, and by looking further down the family, we realized that P2 had to have at least one of the
dominant genes. This is because when we looked at F1 every single plant—all 45 of them—were purple.
Because of this we knew that it must contain a dominant gene (P) and it must contain a recessive gene
(p). This is because the mother could only give a recessive gene. We also know that F1 must contain the
dominant gene because if it didn’t there wouldn’t be any purple plants. Now since F1 has both a
dominant gene and recessive gene, we can conclude that P2 has a dominant gene. We know this
because the mother can only give a recessive gene, which meant that that dominant gene must have
come from the father. Then when we continued on to figure out what the F2 offspring trait genotypes
were. In the F2 family all the plants that phenotype was green had homozygous recessive genes. They
Learning from the Fossil Record
Grade 8 Science
Name: Caroline B.
Date: 1/19/11
had to have homozygous recessive genes because if there was one dominant gene in the combination of
traits the plant would be green. But for the phenotype plants that were purple the genotypes could be
two possibilities. The first possibility is to be a heterozygous pair of genes. That means that it is going to
come out purple because of the dominant gene, but because their parents had heterozygous genes it is
a possibility that the child also has a recessive gene that isn’t showing. The second possibility is to have
homozygous dominant genes. This is because if it is purple it must have one dominant gene in it, and
because their parents both had a dominant gene it is possible for the child to have heterozygous genes.
The F2 purple plants traits are also the possibilities for the P2s purple plants. Those possibilities again
are either heterozygous or homozygous dominant.
We would not have been able to understand how we get traits without Gregor Mendel.
He is the person who had figured out genetics which is also called Mendelian Genetics. Gregor was also
the one to fully explain how we get the genes we do and he also realized that we get our traits by
reproduction. Heredity is what the overall category this is under, and it also means that we get our traits
from our parents through reproduction.