110 Chapter 3 • The Chromosomal Basis of Inheritance chromosome during the metaphase of mitosis is 13 m m. What is the average packing ratio of DNA at metaphase? (Packing ratio 5 length of chromo-some/length of DNA molecule therein.) How is this packing achieved? 17. Boveri said, “The nucleus doesn’t divide; it is divided.” What was he getting at? 18. Galton, a geneticist of the pre-Mendelian era, de-vised the principle that half of our genetic makeup is derived from each parent, one-quarter from each grandparent, one-eighth from each great grandpar-ent, and so forth. Was he right? Explain. 19. If children obtain half their genes from one parent and half from the other parent, why aren’t siblings identical? 20. In corn, the allele s causes sugary endosperm, whereas S causes starchy. What endosperm geno-types result from the following crosses? s / s female 3 S / S male S / S female 3 s / s male S / s female 3 S / s male 21. In moss, the genes A and B are expressed only in the gametophyte. A sporophyte of genotype
This is the end of the preview. Sign up
access the rest of the document.