Heredity

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Heredity

• 10/23/2007

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Essential Question

• What are chromosomes and how do they cause
  mutations?

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Where are we?
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Parent cells vs. Daughter cells

• Parent Cell original cell
• Daughter cell new cells that are made.

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More about chromosomes

• Chromosomes are made of DNA and protein.
• Not visible except during cell division because
  when cells are not dividing they are spread out
  throughout the nucleus called chromatin
• Condense into chromosomes after copied

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The M Phase

• Mitosisdivision of the nucleus
• Parent cell and daughter cells are exactly alike
• cytokinesis

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M Phases

• Phases
• Prophase
• Metaphase
• Anaphase
• Telophase

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Prophase

• Nuclear membrane disappears
• Nucleolus disappears
• Chromatin coils tightly and condenses into
  chromosomes. Each chromosome has 2 chromatids
  held together by a centromere.
• Centrioles move to opposite sides of the cell.
  Asters project from it
• Spindle forms.

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Prophase cont.

• By the end, all the chromatids are attached to
  the spindle (by the centromere) randomly.

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Metaphase

• Chromatids line up along the MIDDLE of the cell.

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Anaphase

• Centromere divides and each chromatid moves to
  opposite poles of the cell.
• (Anaphase apart)

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Telophase

• Opposite of prophase.
• Nuclear membrane reappears.
• Nucleolus reappears
• Spindle breaks down
• Centrioles move back to original location.

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Cytokinesis

• This is not part of mitosis.
• This phase is the splitting of the cytoplasm.
• Can begin during anaphase.
• Plant cells form a cell plate animal cells form
  a cleavage furrow.

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Mitosis

• http//www.phschool.com/webcodes10/index.cfm?fusea
  ctionhome.gotoWebCodewcprefixcbewcsuffix3102
• http//www.cellsalive.com/mitosis.htm

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Cell Division Controls

• Cells will grow until they touch each other
• Cyclins regulate the timing of the cell cycle
• A protein
• Two types of regulator proteins other than cyclin
• Internal Regulators
• External Regulators

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Cancer

• What is cancer?
• Disorder in which some of the bodys own cells
  lose the ability to control their growth.
• Disease of the cell cycle
• Body cells will divide out of control and form
  masses of cells called tumors.
• Malignant tumors are called cancerous tumors
• Cancer cells can break loose and spread
  throughout the body

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Cancer

• Causes of Cancer
• Environmental agents called carcinogens
• Oncogenes cancer genes

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Cancer

• Treatments
• Chemotherapy poisons cancer cells
• Radiation destroys chromosomes
• Surgery to remove the tumor

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Cancer cont

• New treatment include gene therapy
• Introduction of genetic material into a persons
  cells to help fight or prevent disease.
• Nanotechnology
• Science of making things small allows scientists
  to attack the cancer cell
• http//nano.cancer.gov/resource_center/video_journ
  ey.asp

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Mitosis vs. Meiosis
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Meiosis

• Specific Differences
• Phases
• Interphase (not a part of meiosis)
• Prophase 1 Crossing-over occurs the pairing of
  homologous chromosomes forms tetrads
• Metaphase 1
• Anaphase 1 centromere does not divide
• Telophase 1 and Cytokinesis

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Meiosis

• Specific Differences cont
• Prophase 2
• Metaphase 2
• Anaphase 2
• Telophase 2 and Cytokinesis

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Meiosis

• Male animals haploid gametes? Sperm
• Process by which sperm is produced is called
  spermatogenesis
• Female animals haploid gametes? Egg
• Female animals cell division between meiosis I
  and meiosis II are uneven. One gets more
  cytoplasm than other cell
• Other three eggs (little cytoplasm) called polar
  bodies
• Process by which eggs are produced is called
  oogenesis

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Meiosis cont

• http//www.phschool.com/webcodes10/index.cfm?fusea
  ctionhome.gotoWebCodewcprefixcbewcsuffix4114
• http//www.cellsalive.com/meiosis.htm

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Genetic Variation

• Independent assortment
• Crossing-over
• Random fertilization

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Independent Assortment

• Each pair of homologous chromosomes (sister
  chromatid) separates independently of one
  another.
• Meaning about 8 million gene combinations can be
  produced from original cell

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Crossing Over

• DNA exchange between homologous chromosomes
• Adds to genetic variation
• Occurs in prophase of meiosis 1

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Random Fertilization

• Gametes join at random

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Importance of genetic variation

• Essential to evolution
• Example
• Agricultural breeding programs to increase the
  size of domesticated animals