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Transcript
The sequence of growth and division cells undergo 3 main stages Parent cell divides to form two identical daughter cells Period before cell division occurs Longest stage Has three components Growth › Cell doubles in size › Produces structures needed to carry out its functions DNA Replication › Replication a process in which the cell makes a copy of it’s DNA in the nucleus › At the end of this part, a cell has two identical copies of DNA Preparation for Division › Cell produces structures needed during division Stage during which cell’s nucleus divides into 2 new nuclei Has four phases › Prophase, metaphase, anaphase, and telophase Chromatin begins to condense and coil into tiny rods Since the DNA has replicated, each rod is doubled Chromosome doubled rod of condensed chromatin Chromatid one strand of the chromosome Centromere structure holding the two strands of the chromosome together Chromosomes line up across the center of the cell and attach to spindle fiber at the centromere Centromeres split Chromatids separate and move to opposite ends of cell Chromosomes lose their rod like appearance Nuclear membrane forms around each region of chromosomes Final stage in the cell cycle Cytoplasm divides Organelles are distributed into the 2 new cells Each daughter cell has the same number of chromosomes as the parent cell Cell enters interphase and cycle begins again! Depends on type of cell Length of each stage also varies Human brain cells never divide › They get larger and they make more connections › Full size at age 6 DNA looks like a twisted ladder Called a double helix Each rung is made up of molecules called nitrogen bases Adenine pairs with thymine Guanine pairs with cytosine The 2 sides of DNA unwind and separate Separates between base pairs Nitrogen bases floating in nucleus pair up with base on each side The produces two identical copies of DNA