Essential Knowledge 3.A.2

In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization.

The cell cycle is a complex set of stages that is highly regulated with checkpoints, which determine the ultimate fate of the cell. Interphase consists of three phases: growth, synthesis of DNA and preparation for mitosis. The cell cycle is directed by internal controls or checkpoints. Internal and external signals provide stop-and-go signs at the checkpoints. Examples include: mitosis-promoting factor (MPF), action of platelet-derived growth factor (PDGF) and cancer resulting from the disruption in the cell cycle. Cytokins and cyclin-dependent kinases control the cell cycle. Mitosis alternates with interphase in the cell cycle. When a cell specializes, it often enters into a stage where it no longer divides, but it can reenter the cell cycle when give appropriate cues. Nondividng cells may exit the cell cycle; or hold at a particular stage in the cell cycle.

Mitosis passes a complete genome from the parent cell to daughter cells. Mitosis occurs after DNA replication. Mitosis followed by cytokinesis produces two genetically identical daughter cells. Mitosis plays a role in growth, repair, and asexual reproduction. Mitosis is a continuous process observable features along the mitotic process. Mitosis includes replication, alignment, and separation of the chromosomes.

Meiosis, a reduction division, followed by fertilization ensures genetic diversity in sexually reproducing organisms. Meiosis ensures that each gamete receives one complete haploid (1n) set of chromosomes. During meiosis, homologous chromosomes are paired, with one homologue originating from the material parent and the other from the parental parent. Orientation of the chromosome pairs is random with respect to the cell poles. Separation of the homologous chromosomes ensures that each gamete receives a haploid (1n) set of chromosomes composed of both material and paternal chromosomes. During meiosis, homologous chromatids exchange genetic material via a process called "crossing over" which increases genetic variation in the resultant gametes. Fertilization involves the fusion of two gametes, increases genetic variation in populations by providing for new combinations of genetic information in the zygote, and restores the diploid number of chromosomes.

Students should be able to:

LO 3.7 Make predictions about natural phenomena occurring during the cell cycle.

LO 3.8 Describe the events that occur in the cell cycle.

LO 3.9 Construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization.

LO 3.10 Represent the connection between meiosis and increased genetic diversity necessary for evolution.

LO 3.11 Evaluate evidence provided by data sets to support the claim that heritable information is passed from one generation to another generation through mitosis, or meiosis followed by fertilization.