Cell Cycle Recap and Mitosis 2023 PDF

CELL CYCLE RECAP AND MITOSIS Interphase ► Cell grows, develops into a mature, functioning cell, copies its DNA and prepare for division Three phases of interphase include: ► G1 (Growth 1) ► Major period of growth for a cell ► Cell synthesizes new molecules to prepar...

CELL CYCLE RECAP AND MITOSIS Interphase ► Cell grows, develops into a mature, functioning cell, copies its DNA and prepare for division Three phases of interphase include: ► G1 (Growth 1) ► Major period of growth for a cell ► Cell synthesizes new molecules to prepare for next phase ► S (Synthesis) ► Cellular DNA is copied or replicated ► DNA exists as uncondensed fibres called chromatin ► G2 (Growth 2) ► final phase of interphase ► cell synthesizes more molecules prior to mitosis and cell division Cell division THE MITOTIC SPINDLE – a closer look Mitosis ► cell’s copied genetic material separates ► cell prepares to split into two cells ► accurate separation of the cell’s replicated DNA ► four stages: prophase, metaphase, anaphase, and telophase Prophase ► chromatin condenses into chromosomes ► each chromosome exists as two copies of one chromosome ► two chromosomes arms are called sister chromatids ► chromosomes are joined at middle, called centromere ► nuclear membrane breaks down ► nucleolus disappears ► spindle fibres (hollow tube-like structures) form from an area called the centrosome ► spindle apparatus = spindle fibres and centrosome ► Astral rays radiate from centrioles (organize contents of cytoplasm by holding them in position) ► Centrioles move to poles Metaphase ► Spindle fibres from opposite poles attach to chromosome at the centromere forming the kinetochore ► spindle fibres guide the chromosomes to the equator of the cell ► (each pair of sister chromatids are considered a single chromosome as long as chromatids remain joined at centromere) Anaphase ► Spindle fibres shorten, pulling apart the centromeres and the chromosomes ► Dyad splits into 2 separate chromatids (now referred to as chromosomes) ► Spindle fibres pull each chromosome to opposite poles ► End result: one complete set of chromosomes at each end  Telophase ► Begins when chromosomes have reached opposite poles ► All the processes that are the opposite of prophase ► Chromosomes unwind into chromatin (less visible) ► Nuclear membrane reforms around new set of chromosomes and nucleolus forms within each nucleus ► Spindle fibres break down ► Astral rays breakdown Cytokinesis In plant cell: In animal cell: ► Division of the cytoplasm ► Cell wall is stronger than the ► Indentation forms in the cell membrane of animal cell membrane along equator of and does not pinch cell until cell is pinched into two; microfilaments constrict ► Cell plate forms between the cytoplasm the two daughter nuclei ► Cytoplasm divides equally ► Cell walls form on either ► Ends with separation of the two genetically identical side of the plate daughter cells Cell cycle checkpoints  Prokaryotic cells: ► Do not have a nucleus ► Complete cell division through binary fission ► Once prokaryotic DNA is duplicated, both copies attach to cell membrane ► As membrane grows, attached DNA pulls apart ► Cell completes fission producing two new cells