Download Mendel`s Experiments

Mendel’s Experiments
Page 35
Gregor Mendel
Read the section titled “Who was Gregor Mendel?”
on page 56 and answer these questions in your
notebook.
(answer complete sentences that include part of the question)
1. When and where was Gregor Mendel Born?
2. Where did he learn about flowers and fruit
trees?
3. When he was 21 years old, what did he do?
4. What did Mendel go to school to study?
5. After Mendel failed his final exam, what did he
do?
6. What did Mendel discover?
7. Where did Mendel make his discovery?
Mendel’s First Experiment
• Put the green paper with the “Mendel’s 1st
experiment” side facing up. Open the
envelope labeled PARENTS and place the two
plant “parents” in the correct spaces on the
green paper.
• In this experiment, Mendel chose each of the
parent plants because it was true-breeding
(purebred) for a characteristic. He had
created true-breeding plants by selfpollinating plants until he always got offspring
that looked just like the parent.
• Mendel wondered what the offspring would look
like if he “crossed” (cross-pollinated) these two
parents. In genetics, the fist generation is called
the F1 generation.
• Open the envelope labeled F1 GENERATION and
place the offspring in the labeled spaces.
• In your notebook sketch what you see on your
green paper.
• Compare the parents and F1 offspring.
• Under your sketch write what you notice about
the parents and the 4 offspring.
• Compare your results with the tables around you.
What do your results have in common with the
tables around you?
• The results of Mendel’s first experiment
showed a single trait consistently showed up
in the F1 generation of offspring and the
other trait consistently disappeared.
• He called the trait that showed up dominant,
and the trait that did Not show up recessive.
• Mendel hypothesized that the recessive
“factor” was still there, but was being
covered up by the dominant “factor”.
• What Mendel called “factors” we now call
“genes”
PUT THE PARENTS AND F1 OFFSPRING BACK IN
THEIR CORRECT ENVELOPES.
Mendel’s 2nd Experiment
• Mendel next wondered what would happen if
he self-pollinated the F1 generation. Let’s look
at what he discovered.
• Turn the Experiment paper over. Take out one
of the F1 generation plants and put it in the
correct space.
• You only need one parent plant because it will
be self-pollinated.
• Examine the parent plant- is it showing a
dominant or a recessive trait?
• Remember- Mendel hypothesized that the F1
generation plants had both a dominant and a
recessive factor, but that the dominant gene is
covering up the recessive gene.
• If this is true, then what type(s) of genes are
present in the F1 plant? -Discuss with your
shoulder partner.
• Open the envelope labeled F2 GENERATION
and place the offspring in the labeled spaces.
• Sketch what you see on your green paper.
• Compare the F1 parent and F2 offspring.
• Under your sketch write what you notice
about the parent and the offspring.
• Compare your results with the tables around
you. What do your results have in common
with the tables around you?
• Results- Mendel’s 2nd experiment
demonstrated that the recessive trait seemed
to show up again in the F2 generation, even
though it didn’t seem to be present in the F1
generation.
• Mendel also thought that the plants showing
the recessive trait must have inherited two
recessive “factors” (genes) since the trait was
not being masked by the presence of a
dominant gene.
The Big Picture
• If you inherit one dominant and one recessive
gene for a characteristic such as eye color,
DOMINANT
then the ________________
trait will show.
• If you inherit two dominant genes, then the
_______________
will show.
DOMINANT
• If you inherit two recessive genes, then the
RECESSIVE
_______________
will show.
Bottom Line
• How could a child be born with blue eye
(recessive trait) when both parents have
brown eyes ( dominant trait)?