The Cell Cycle Multicellular organisms constantly make new cells from _______________ cells. Making new cells allows organisms to __________ and replace cells that have __________. The Life of a Cell: : Cells pass through different stages in their life cycle. Cell cycle – The life cycle of a cell. The cell cycle begins when the cell is _______________ and ends when the cell _______________ and forms new cells. Before a cell divides, it must copy its ______. The DNA of a eukaryotic cell is located in the ___________________ on structures called chromosomes. Chromosomes – In a eukaryotic cell, one of the structures of the nucleus that are made up of DNA and protein; in a prokaryotic cell, the main ring of DNA. Copying chromosomes ensures that each new cell will be an exact _________ of its parent cell. Making More Prokaryotic Cells: Cell division in prokaryotic cells involves ____________ ____________, which means “splitting into two parts”. The result of binary fission is two cells that each contain one copy of the circular DNA. Prokaryotic cells reproduce by binary fission because they are less _______________ than eukaryotic cells. Eukaryotic Cells and Their DNA: The chromosomes of eukaryotic cells contain more DNA that those of prokaryotic cells do. Different kinds of eukaryotes have different numbers of chromosomes. The number of chromosomes an organism has has nothing to do with the ______________________ of the organism. EX: fruit flies have 8 chromosomes humans have 46 chromosomes potatoes have 48 chromosomes An organism’s chromosomes are matched up in pairs called ____________________________ chromosomes. Homologous chromosomes – Chromosomes that have the same sequence of genes and the same structure. EX: Humans have 46 chromosomes so they have 23 pairs of homologous chromosomes. (46 ÷ 2 = 23) Making More Eukaryotic Cells: Three Stages of the Cell Cycle: Interphase Mitosis Cytokinesis o Interphase – The cell grows and ________ its organelles and chromosomes. After each chromosome is duplicated, the two copies are called ______________________. Chromatids are held together at a region called the _________________. The joined chromatids twist and condense into an ”X” shape. o Mitosis – The complicated process of chromosome ______________________ in eukaryotic cells. When mitosis is complete, each new cell has a copy of each ___________________________. Mitosis is divided into four phases: (PMAT) • P____________________ • M____________________ ____________________ • A____________________ • T____________________ o Cytokinesis – The _____________________ of the cytoplasm of a cell. In animal cells, cytokinesis takes place by pinching in the cell membrane until two daughter cells are formed. In eukaryotic cells with a cell wall, a ____________ ____________ forms in the middle of the cell. After the cell splits in two, a new cell wall forms where the cell plate was. * The result of cytokinesis is two new daughter cells that are _____________ to each other and to the original cell. These cells now enter interphase and the ________ _________ resumes.
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