the chicks and mouse would be losely conected because they have more of the same gentic material and fish and humans would havwe the same since they kind act like the same because The recent advances in developmental biology described have established the central importance of a small number of highly conserved signal transduction pathways that mediate cell interactions crucial for animal physiology, reproduction, and development. It seems likely that many developmental toxicants might affect development by acting on those pathways. Application of the methods that have been so successful in elucidating them should now allow scientists to investigate that possibility and to determine the mechanisms by which developmental toxicants act. This chapter reviews the experimental approaches primarily responsible for the recent advances in knowledge about animal development and discusses how those approaches might be applied to developmental toxicology. Chapter 8 discusses how those approaches might lead to improved qualitative and quantitative risk assessment.
In Macbeth, the witches in Act I foretell the future of Macbeth as king and Banquo as the first of a line of kings. In Act IV, the witches foreshadow Macbeth's downfall.
In mitosis a cell divides to form two identical daughter cells. It is important that the daughter cells have a copy of every chromosome, so the process involves copying the chromosomes first and then carefully separating the copies to give each new cell a full set.
