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groups of cells in the blastula are synchronized to divide at the same time through mitosis. Some of these cells will eventually give rise to the sand dollar's germ cells. Others will play important roles in various developmental processes, such as cell differentiation, the formation of the digestive system, and the development of the exoskeleton. Despite their different characteristics and roles, all of the sand dollar's cells (except for eggs or sperm) are genetically identical due to mitosis.

overview of the effects of different types of drug and alcohol use during pregnancy

Explore eight different mutations with graphics, gene explanations, and phenotypic effects.

This video segment adapted from NOVA scienceNOW examines the realm of personal DNA testing. It describes the latest tests, which look for single-nucleotide polymorphisms (SNPs). These single-letter differences in DNA sequence make humans unique from one another but may also predispose people to certain diseases. The video also discusses the Personal Genome Project, an extension of the Human Genome Project aimed at determining the root causes of many common diseases. The Personal Genome Project takes into account personal genomics as well as lifestyle information, such as one's living environment, habits, and behaviors.

By observing how the cells in the zebrafish's skin responded to injury, the Duke team learned a lot about the skin regeneration process and were surprised by its complexity. They saw that in the hours following a fin amputation, for example, zebrafish regenerated skin through three different mechanisms: the "recruitment" of spare skin cells from other areas, a temporary doubling in size in some pre-existing cells, and the creation of completely new cells.