4.6 Cell Cycle

Heritable information provides for continuity of life. Describe the events that occur in the cell cycle. In eukaryotes, cells divide and transmit genetic information via two highly regulated processes. The cell cycle is a highly regulated series of events for the growth and reproduction of cells-- The cell cycle consists of sequential stages of interphase (G1, S, G2), mitosis, and cytokinesis. A cell can enter a stage G0 where it no longer divides, but it can reenter the cell cycle in response to appropriate cues. Nondividing cells may exit the cell cycle or be held at a particular stage in the cell cycle. Explain how mitosis results in the transmission of chromosomes from one generation to the next. Mitosis is a process that ensures the transfer of a complete genome from a parent cell to two genetically individual daughter cells-- Mitosis plays a role in growth, tissue repair, and asexual reproduction. Mitosis alternates with interphase in the cell cycle. Mitosis occurs in a sequential series of steps (prophase, metaphase, anaphase, telophase).

cell division

• every cell arises from a pre-existing cell, all cells have the ability to grow and multiply

• cells transmit genetic information via cell division

• basis for asexual reproduction, tissue repair, growth

somatic cell cycle

• non-reproductive, results in identical DNA

• three phases: interphase, mitosis, cytokinesis

• most cells spend time in interphase, carrying out regular activities

• G0 - stage where the cell no longer divides, can reenter cell cycle in response to appropriate cues

interphase

cells grow nad prepare to divide, longest phase, 3 phases

• Gap 1 (G1) - longest growing phase, some organelles replicated

• Synthesis (S) - cell replicates its genetic material, each chromosome becomes two sister chromatids held together by the centromere

• Gap 2 (G2) - growth continues, cell prepares for division

mitosis

division of the nucleus, alternates with interphase, 5 phases

• prophase - chromatin condenses into chromosomes, nucleoli disappear, spindle fibers appear and attach to the kinetochore (centromere part) of each chromatid

• metaphase - chromosomes line up at metaphase plate

• anaphase - sister chromatids are pulled apart to opposite ends, spindle fibers shorten

• telophase - nuclear membrane and nucleoli reappear, spindles depolymerize

cytokinesis

cells physically divide into two daughter cells

• animal cells - cleavage furrow appears

• plant cells - cell plate becomes new cell wall