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 1 st 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 self- pollinating 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 2 nd 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 2 nd 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, then the ________________ trait will show. If you inherit two dominant genes, then the _______________ will show. If you inherit two recessive genes, then the _______________ will show. Bottom Line How could a child be born with blue eye (recessive trait) when both parents have brown eyes ( dominant trait)? DOMINANT RECESSIVE