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Chapter 10: Cell Growth and Division 10.2 - The Process of Cell Division Mr. M. Varco Saint Joseph High School Chromosomes • What role do chromosomes have in cell division? • Prior to cell division, parent cells must undergo DNA replication so that each daughter cell gets a complete copy of genetic information. • All cells, including bacteria, have a tremendous amount of DNA that must be carefully packaged. Chromosomes • The cell’s genetic information is bundled into packages of DNA known as chromosomes • Chromosomes make it possible to separate DNA precisely during cell division • The cells of every organism have a specific # of chromosomes Chromosomes Prokaryotic Chromosomes • Most prokaryotes contain a single, circular DNA chromosome that contains nearly all of the cell’s genetic information Chromosomes Eukaryotic Chromosomes • Eukaryotic cells generally have more DNA than prokaryotes and therefore contain multiple chromosomes • Humans cells have 46 chromosomes Chromosomes Eukaryotic Chromosomes • Chromosomes are located in the nucleus and are made up of chromatin • Chromatin is composed of chromosomes and histone proteins Chromosomes Eukaryotic Chromosomes • DNA tightly coils around histone proteins, forming nucleosomes • Cells package their information in chromosomes to ensure equal division of DNA when a cell divides The Cell Cycle • During the cell cycle, a cell: grows, prepares for division, and divides to form two daughter cells The Cell Cycle Prokaryotic Cell Cycle • The prokaryotic cell cycle is a regular pattern of growth, DNA replication, and cell division • The process of cell division is a form of asexual reproduction called binary fission The Cell Cycle Eukaryotic Cell Cycle • The eukaryotic cell cycle consists of 4 phases: G1, S, G2, and M The Cell Cycle Eukaryotic Cell Cycle • During the G1 phase, cells do most of their growing, which includes increasing in size, as well as synthesis of proteins and organelles The Cell Cycle Eukaryotic Cell Cycle • During the S phase, new DNA is synthesized when the chromosomes are replicated. • The cell contains twice as much DNA as it did at the beginning of the cell cycle The Cell Cycle Eukaryotic Cell Cycle • During the G2 phase, many of the organelles and molecules required for cell division are reproduced • The is the shortest of the three phases, and marks the cell as ready for division The Cell Cycle Eukaryotic Cell Cycle • The M phase, which follows interphase, produces two daughter cells • Unlike interphase, the process of cell division occurs very quickly The Cell Cycle Eukaryotic Cell Cycle • In eukaryotes, cell division occurs in two main stages: - Mitosis: the division of the cell nucleus - Cytokinesis: the division of the cytoplasm Mitosis Prophase: • The first phase of mitosis, in which chromatin condense and become visible chromosomes • The duplicated strands of DNA attach at an area called the centromere • Each DNA strand in the duplicated chromosome is referred to as a chromatid Mitosis Prophase: • The cell starts to build a spindle, used to help separate the chromosomes at the centromere • Spindle fibers extend from regions where tiny paired structures called centrioles are located Mitosis Metaphase: • The second phase, where centromeres of the duplicated chromosomes line up across the center of the cell • Spindle fibers connect the centromere of each chromosomes to the two poles of the spindle Mitosis Anaphase: • The third phase, when centromeres are pulled apart and the sister chromatids separate to become individual chromosomes • The chromosomes move along spindle fibers to opposite ends of the cell Mitosis Telophase: • The forth phase, during which the chromosomes begin to spread out into a tangle of chromatin • Spindle fibers break apart, and the nuclear envelope re-forms around each cluster of chromosomes