Investigating Monohybrid and Dihybrid Crosses
Once you understand Mendel's ideas, it becomes possible to make effective predictions about patterns of inheritance for some traits
in some organisms. In the following passage, you will be introduced to monohybrid and dihybrid crosses, two types of matings that are important to geneticists. You will also learn how to use a Punnett square to analyze matings.
As you read the passage, think about the new terms and concepts you are learning. After you have finished the reading, complete the crossword puzzle below in order to test your knowledge.
Reading Assignment 8: Monohybrid and Dihybrid Crosses
Read pages 197-200 in the Foundations of Modern Biology Textbook, Solomon, Berg, and Martin's Biology.
Ready for a Review?
Your Personal Journal (Entry 17)
After you have finished reading, the following questions will help you to focus on the most important concepts in the passage. In your journal, answer each of these questions. Use the TCQC Short-Answer Response Format. Then read each question with your mentor, and use it to open a discussion.
Questions to Open Discussion:
- What does it mean to say that an organism is homozygous for a given trait? What does it mean to say that an organism is heterozygous for a given trait?
- What is a genotype? Give an example of a situation in which two organisms might have identical phenotypes but different genotypes.
- Each parent contributes the same amount of genetic material to a child, yet the child may resemble one parent more than another. How is this possible?
- What is a Punnett square? Explain what the Punnett square shows.
- What is a test cross? When would a breeder need to perform a test cross?
- How does a dihybrid cross differ from a monohybrid cross? Can a dihybrid cross be modeled using a Punnett square? How would the Punnett square for a dihybrid cross differ from one for a monohybrid cross?
- What is the principle of independent assortment? Why is the principle of independent assortment important when we consider dihybrid crosses? Could basic Punnett squares be used to make predictions about dihybrid crosses if the principle of independent assortment did not hold true?
Do you understand everything so far? Soon you will be solving genetic problems. If you feel a little unsure about the terminology, you may want to review some more with your mentor before proceeding!
