The Work of Gregor Mendel Guided Reading
Gregor Mendel 25 min Mendel (pearson) 6 min
The Experiments of Gregor Mendel 1. What is Heredity? The delivery of characteristics from parents to offspring 2. What is Genetics? the science of the study of heredity 3. The modern science of genetics was founded by an Austrian monk named Gregor Mendel 4. What plant did Mendel use in his experiments? Why? Pea plants they are easy to grow
The Role of Fertilization 5. Describe the reproductive structures of a flower. the male parts produce pollen, which contain sperm, and the female parts produce eggs 6. What happens during fertilization? the male and female reproductive cells join to produce a new cell, which develops into an embryo 7. What does self-pollinating mean? the sperm cells (pollen) fertilize the egg cells within the same flower, which can produce offspring identical to the parent plant
8. The plants in Mendel s garden were true-breeding which means that they were self-pollinating and would produce offspring identical to themselves 9. A trait is a specific characteristic of an individual, such as seed color or plant height. 10. Many traits vary from one individual to another.
11. What did Mendel do to learn how traits were determined? He cross-pollinated his true breeding plants by dusting the pollen of one plant onto the female parts of another flower. He crossed a plant showing one version of the trait with a plant showing the other version. 12. Mendel studied seven different traits of pea plants. Each of these seven traits had two contrasting characteristics, such as green seed color or yellow seed color. 13. What are hybrids? offspring of crosses between parents with different traits
Genes and Alleles 14. When doing genetic crosses, what are the original pair of plants called? P (parental) generation 15. The offspring of the P generation are called the F1, or first filial, generation 16. After Mendel crossed two plants (P generation), what were the F1 plants like? for each trait he studied, all of the offspring had the characteristic of only one of its parents. The other trait seemed to have disappeared
17. What was Mendel s first conclusion? An individual s characteristics are determined by factors that are passed down from one parental generation to the next 18. What are these factors now called? Genes 19. What are alleles? Give an example. The different forms of a gene. Plant height has two alleles tall and short.
Dominant and Recessive Alleles. 20. What was Mendel s second conclusion? The principle of dominance 21. The principle of dominance states that some alleles are dominant and others are recessive. 22. An organism with at least one dominant allele for a particular trait will exhibit that form of the trait.
23. An organism with a recessive allele for a particular trait will exhibit that form only when the dominant allele for the trait is not present 24. For the plant height trait, which allele is dominant and which is recessive? Tall is dominant to short height
Segregation 25. After producing the F1 generation, what was Mendel s question? had the recessive alleles simply disappeared, or were they still present in the new plant? 26. What are the offspring of the F1 plants called? How did he produce them? F2 generation he self-fertilized the F1 plants
The F1 Cross 27. What was Mendel s discovery when comparing the F2 plants? the traits cotrolled by the recessive alleles reappeared in the second generation 28. What amount (percentage) of the F2 generation had the recessive trait? one fourth (25%)
Explaining the F1 Cross 29. What did Mendel initially assume? dominant allele masked the recessive allele in the F1 generation 30. What did the reappearance of the recessive trait indicate? The recessive allele had separated from the dominant allele 31. What are gametes? sex (reproductive) cells sperm and eggs
The Formation of gametes 32. What happens to an individual s alleles during gamete formation? the alleles for each gene segregate from each other, so that each gamete only carries one allele for each gene 33. When do the alleles pair up again? (see Figure 11-5) during fertilization