514 Introduction to the Study of Science 



tallness of peas, are not blended in hybrids. In the first generation 

 the dominant character alone appears. In the second generation the 

 recessive character appears in one out of four individuals. 



By selections made in accordance with Mendel's law desirable 

 characters can be fixed and undesirable characters eliminated. An 

 example is the production of a new variety of wheat having the desir- 

 able characters of domestic and wild wheat. 



REVIEW QUESTIONS 



1. In what field of knowledge was Mendel an investigator? In 

 what way are his methods and results important? 2. Give a brief 

 statement of the life and work of Gregor Mendel. 3. What plant 

 did Mendel choose for his experiments? Why? 4. Mention some 

 characters of the pea. 5. Did Mendel find that these characters 

 in hybrids blended or mixed? 6. (a) Mention several "unit char- 

 acters." (6) Define the term. 7. How does a plant resemble a 

 mosaic ? 8. (a) What result is seen in the hybrids of purple and white 

 peas? (6) In the succeeding generations what colors appear? 

 (c) What use may be made of the facts? 9. (a) Describe Mendel's 

 experiment with hybridizing dwarf and tall peas. (6) Which of the 

 two characters, tallness and dwarfishness, is the dominant? (c) What 

 is the other called? (d) Explain each term. 10. (a) What results 

 appeared in the offspring from hybrids? (6) Which of the two 

 varieties produced true to type? (c) What results were obtained by 

 planting seeds of tall hybrids? 11. Summarize the results of planting 

 seeds of the recessives and seeds of the dominants. 



12. (a) With what other kinds of plants has Mendel's law been 

 demonstrated? (6) What kinds of animals? 13. How is Mendel's 

 law illustrated in the color of human eyes? 14. Why is it so difficult 

 to apply the Mendelian law to human heredity? 15. What is the 

 ratio in the offspring of a hybrid between those showing the dominant 

 and those showing the recessive character? 16. What advantages 

 may be gained by applying Mendel's law to plant and animal breeding ? 



17. What use could be made of a plant that is found to be im- 

 mune to a prevailing disease? 18. (a) What are the important char- 

 acters of the wild wheat of Palestine? (6) What use is being made 

 of these characters in the improvement of domestic wheat ? 19. Men- 

 tion some characters desirable in cultivated plants. What has to be 

 done in order to combine them in one individual? In one variety? 



