9. Mitosis and Meiosis

Contrast spermatogenesis and oogenesis. What is the significance of the formation of polar bodies?

During oogenesis in an animal species with a haploid number of 6, one dyad undergoes nondisjunction during meiosis II. Following the second meiotic division, this dyad ends up intact in the ovum. How many chromosomes are present in (a) the mature ovum and (b) the second polar body? (c) Following fertilization by a normal sperm, what chromosome condition is created?

Wolves and coyotes can interbreed in captivity; and now, because of changes in their habitat distribution, they may have the opportunity to interbreed in the wild. To examine this possibility, mitochondrial DNA from wolf and coyote populations throughout North America—including habitats where the two species both reside—was analyzed, and a phylogenetic tree was constructed from the resulting data (see Section 1.4 for details on how this is accomplished). Sequence from a jackal was used as an outgroup and a sequence from a domestic dog was included, demonstrating wolves as the origin of domestic dogs. What do you conclude about the possibility that interspecific hybridization occurred between wolves and coyotes on the basis of this phylogenetic tree?