Module 6 Mendelian Genetics

Explore

Read

Early Theories

Farmers have always known that keeping seeds back from good crops, or breeding prize cows or chickens, helps to improve the next generation’s chances of yielding better numbers and/or favorable traits, or of being better in some other way. However, just exactly how favorable traits are passed on has been the interest of scientists for centuries. Early theories tended to give importance to the kind of life the parents lead. Similar to Lamarkian’s ideas of evolution where body parts change in response to use, many early scientists believed life’s experiences affected the next generation’s traits. These theories were finally put to rest by a 19th century Austrian monk named Gregor Mendel. Mendel studied garden peas as his experimental subjects and, with breeding and observation, laid the foundation of our current knowledge and understanding of heredity.

Read the sections on “Early Theories of Inheritance” and “Developing a Theory of Inheritance: Gregor Mendel’s Experiments” in your textbook on pp. 586–588. When finished your reading, answer the following questions for your own understanding and save the answers into your course folder.

1. Where did Aristotle believe the factors for inheritance were located in the body? How did he believe these were passed down?

2. What were some of the likely problems early scientists must have encountered when trying to explain inheritance?

3. Examine the seven traits Mendel studied on p. 588. What do you notice about all of them?

4. What is a monohybrid cross?

5. Explain how a hybrid plant is different from a true breeding plant.

6. Explain the difference between P, F1, and F2 generations in a cross.

Watch and Listen

Consider the first part of the following video on Classical Genetics and Monohybrid Crosses. (15 minutes). Begin the video and continue watching until you reach the section “Bio Challenge: Round vs. Wrinkled Peas.” Answer the following questions for your own understanding and save the answers in your course folder.

1. Who discovered that cells differentiate during embryo development and disproved the idea that the egg or sperm held a complete miniature organism?

2. Explain the meanings of the terms dominant and recessive factors (we now call factors alleles).

3. Distinguish between the terms gene, allele, and chromosome.

4. What process creates gametes?

5. How do we distinguish between dominant or recessive alleles when drawing them on a chromosome or in a Punnett square.

6. What does it mean to be homozygous for a trait? How is this different from being heterozygous for a trait?

7. Using an example, distinguish between the terms genotype and phenotype.

Web Search

The following video reviews Mendel’s experiments.

1. Why did Mendel choose to study pea plants in his experiments?

2. How did he ensure that his plants were true breeding?

3. What does Filial mean?

4. How did Mendel make sure his results were statistically accurate?