594 GENETICS AND EVOLUTION 



of the egg. Wlicn a hen from the 90 gram strain is mated with a rooster from the 30 

 gram strain, the hens in the F-, generation lay eggs weighing 60 grams. If a hen and 

 rooster from this h\ generation are mated, what will be the weights of the eggs laid 

 by the hens of the ¥2 generation? 



6. Mrs. Doe and Mrs. Roe had babies at the same hospital and at the same time. Mrs. 

 Doe took home a girl and named her Nancy. Mrs. Roe received a boy and named him 

 Harry. However, she was sure that she had had a girl and brought suit against the 

 hospital. Blood tests showed that Mr. Roe was type O, Mrs. Roe was type AB, Mr. and 

 Mrs. Doe were both type B, Nancy was type A and Harry was type O. Had an ex- 

 change occurred? 



7. A woman who is type O and rh negative is married to a man who is type AB and rh 

 positive. The man's father was type AB and rh negative. What are the genotypes of 

 the man and woman and what blood types may occur among their offspring? Is there 

 any danger that any of their offspring may have erythroblastosis fetalis? 



8. What are the advantages and disadvantages of inbreeding? 



9. A certain recessive trait occurs in a human population with a frequency of about 1 

 in 10,000. What proportion of the population are heterozygous for this gene? 



10. Discuss the evidence that desoxyribonucleic acid is an integral part of the gene. 



11. Differentiate between chromosomal and point mutations. How would you define a 

 mutation? 



12. Discuss the evidence which has led to the abandonment of the theory of the inheri- 

 tance of acquired characters. 



Supplementary Reading 



Two more advanced texts of genetics are Sturtevant and Beadle, An Introduction to 

 Genetics, and Sinnott, Dunn and Dobzhansky, Principles of Genetics. Genetics in the 

 Twentieth Century, edited by L. C. Dunn, is a collection of papers presented at the 

 Golden Jubilee of Genetics on the 50th anniversary of the rediscovery of Mendel's work. 

 Some articles of special interest are those on the history of genetics by H. litis, C. Zirkle, 

 W. E. Castle and H. J. Muller, one by R. B. Goldschmidt on the relations of genetics to 

 other sciences, one by G. W. Beadle on chemical genetics, and those on practical applica- 

 tions of genetic knowledge by L. H. Snyder, J. W. Gowen, C. C. Little, A. Miintzing, 

 J. L. Lush, J. C. Walker and P. C. Mangelsdorf. The Chemical Basis of Heredity, edited 

 by W. D. McElroy and B. Glass, presents the discussions of a symposium held in June 

 1956. Although some of the discussions are rather advanced, there is much of general 

 interest in the book. 



