The Cellular Basis of Inheritance

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The Cellular Basis of Inheritance

• Sections 9.1, 9.2, and 9.4

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Cell Division Enables Living Things to

• Repair damage
• Replace lost or damaged cells
• Grow
• Increase in size
• Produce offspring
• Replicate entire organisms

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Cell Reproduction

• Asexual Reproduction
• Single cell division in which a single cell or
  group of cells each duplicates into two new
  genetically identical cells which receive all of
  the genetic material
• Sexual Reproduction
• When two parents are involved in the production
  of offspring and the offspring have a combination
  of genetic material from each of the parents

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Asexual Reproduction
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Sexual Reproduction
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Chromatin

• The genetic material found in the nucleus exists
  as a mass of long, microscopic fibers that
  consist of chromatin
• Chromatin - the combination of DNA and protein
  molecules

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Preparing to Divide

• Chromatin fibers condense and become visible as
  compact structures called chromosomes.
• Before cell division begins, a cell duplicates
  all of its chromosomes

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Structure of Chromosomes

• Each chromosome contains two identically joined
  copies called sister chromatids
• Centromere - area where the two chromatids are
  joined together

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During Division

• Each human cell contains 46 chromosomes.
• A dividing cell starts with 46 pairs of
  duplicated chromosomes - each made up of 2 sister
  chromatids
• When the cell divides, the sister chromatids
  separate from each other.
• The result is two offspring nuclei, each
  containing 46 chromosomes

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The Cell Cycle

• How often a cell divides depends on the type of
  cell - some divide often and some not at all.
• Cell Cycle - extends from the birth of the cell
  to the time the cell itself reproduces

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Interphase

• In this stage, the cell carries out its metabolic
  processes and performs any necessary functions
  including the following
• Increasing its supply of proteins
• Increasing its number of organelles
• Growth
• Cellular functions leading up to cell division
• The cell may spend as much as 90 of the cell
  cycle in this stage

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Cellular Functions Leading Up to Cell Division
Include

• S Phase (Synthesis) - the duplication of the DNA
  in the cells chromosomes
• G2 Phase (Gap Phase) - each duplicated chromosome
  remains losely packed as chromatin fibers and
  gets ready to divide
• G1 (Gap Phase) - cell grows

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• Cell Cycle Animation

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Mitotic Phase

• The stage of the cell cycle when the cell is
  actually dividing
• An accurate way of distributing identical copies
  of a large amount of genetic material to two
  daughter cells -- errors rarely occur
• Unique to eukaryotes
• Two processes
• Mitosis
• Cytokinesis

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Mitosis and Cytokinesis

• Mitosis the nucleus and the duplicated
  chromosomes divide and are evenly distributed,
  forming two genetically identical daughter cells
  with a single nucleus, cytoplasm, and a plasma
  membrane
• Cytokinesis the process by which the cytoplasm
  is divided in two usually begins when mitosis
  has been completed

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The Cell Cycle and Cancer Cells

• The timing of cell division is important
• A control system directs the sequence of events
  in the cell cycle.
• When the control system malfunctions, cells may
  reproduce at the wrong time, in the wrong place,
  or in the wrong way.
• Cell Cycle Control Animation

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Tumors and Cancer

• Out of control cell reproduction can produce a
  mass of cells called a tumor.
• Benign tumor - an abnormal mass of essentially
  normal cells
• Malignant tumor - masses of cells that result
  from the reproduction of cancer cells
• Cancer - a disease caused by the severe
  disruption of the mechanisms that normally
  control the cell cycle can lead to uncontrolled
  cell division and can result in death.

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Cancer Treatment Options

• Surgery
• Difficult to remove all traces of cancer
• Radiation
• Can damage other cells
• Chemotherapy
• Can affect the intestinal cells or hair follicle
  cells difficult side effects
• Two types of antimitotic