5-3-18 Identifying Dominant Traits

Do Now: Take out your homework Do Now: Take out your homework. Read the handout of “Mendel’s Conclusions”. Answer the following questions in your lab notebook. What is a dominant trait? What is a recessive trait? A dominant trait is a genetic factor that blocks another genetic factor. A recessive trait is a genetic factor whose expression is blocked by the presence of a dominant factor. What did Mendel conclude about inherited traits? Mendel concluded that two factors control each inherited trait. A sperm cell contributes one factor and an egg cell contributes the other. How do dominant and recessive factors interact? One dominant factor blocks a recessive factor. Two recessive factors are required for the recessive trait to be expressed.

HW Review – What did Mendel conclude about inherited traits? 1. R 2. D 3. D 4. R 5. R 6. D 7. D 8. R 9. R 10. D 11. T 12. T 13. F

HW Review – How do dominant and recessive factors interact? 1. B all purple-flower plants 2. C mostly purple-flower plants 3. C half purple-flower plants and half white-flower plants 4. because those are recessive traits that are blocked by the dominant traits of long stems, yellow seeds, and smooth pods 5. a. 75 percent 5. b. 25 percent

Mini Lab: Which is the dominant trait? Purpose: To reinforce the concept of dominant and recessive genetic traits This lab models one of Mendel’s experiments. Recall that Mendel crossed plants that were true-breeding to make the first generation of offspring and crossed the resulting hybrids to obtain the second generation. Use the data provided to determine which trait is dominant. Answer the “Analyze and Conclude” questions. You may work with your shoulder partner.

Mini Lab: Which is the dominant trait? Axial flower position, smooth pea pods, long stems, and yellow seeds are dominant; terminal flower position, bumpy pea pods, short stems, and green seeds are recessive. The recessive trait (such as terminal flowering plants) are absent in the first generation and reappear in the second generation. Only the dominant trait (such as axial flower position) showed up in the first generation.

Homework: Study for the quiz which will be on Monday, 5/7