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The Cell Cycle Brought to you by: Today’s Lesson Is brought to you by the letter And the numbers C 23 and 46 Important Vocabulary • Chromatin: Long, tangled strands of DNA found in the cell nucleus during Interphase • Chromosomes: Structures that carry the genetic material that is copied and passed from generation to generation of cells. Humans have 23 pairs of chromosomes; 46 total chromosomes • Chromatids: Chromosomes duplicate during S phase and are attached by a centromere. The two copies are called chromatids. Chromatids & Centromere Vocab. Continued . . . • Centromere: Cell structure that joins the two chromatids. • Homologous Chromosomes: Paired chromosomes with genes for the same traits, structure and function. Humans have 23 Homologous Chromosomes. • Parent Cell: Original cell in interphase, before division occurs. • Daughter Cell: Cells produced from parent cell at the end of the cell cycle. Cell Cycle • Made up of 3 Phases – Interphase – Mitosis – Cytokenesis Interphase • • • • Cell spends 90% of its lifetime in interphase G1 phase: cell grows S phase: DNA (chromosomes) replicate G2 phase: cell prepares to divide Mitosis • Occurs AFTER interphase is finished • Consists of 4 phases: – – – – Prophase Metaphase Anaphase Telophase Prophase • Early – chromatin coil up and become chromosomes. Each crhomosomes is made up of 2 identical parts called chromatids joined by a centromere • Mid – nuclear envelope begins to disappear • Late – nuclear envelope gone and centrioles move towards poles as spindles form. Metaphase • Early – centrioles at poles and spindle fibers attach to centromeres of chromosomes • Mid – chromosomes in the process of lining up along the equator of the cell • Late – chromosomes lined up along equator of cell. Anaphase • Early – Centromeres split apart as spindles bring chromatid pairs towards opposite poles • Mid – chromatids moving closer to opposite poles • Late – chromatids at opposite poles Telophase • Early – Nuclear envelope begins to form • Late – 2 distinct daughter cells are formed Can you guess what my favorite phase is? Telly – phase! Cytokenesis • Cytoplasm divides • IN PLANTS: cell plate forms between cells, cell membrane forms around each side of cell plate, and cell wall forms around membrane • IN ANIMALS: cell membrane pinches off between old and new cell, creating 2 separate cells Let’s count how many daughter cells come from 1 parent cell! 1. . . . 2. . . . . 2 daughter cells!
