Meiosis

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Meiosis

• Gamete Formation

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Homework

• Complete Graphing handout
• And
• 11-4 in Guided Reading Workbook

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Reproduction

• Asexual reproduction - Asexual reproduction is
  the formation of new individuals from the cell(s)
  of a single parent. The new cell (daughter cell)
  is usually identical to the parent.
• Sexual reproduction - In sexual reproduction, two
  individuals produce offspring that have genetic
  characteristics from both parents. Sexual
  reproduction introduces new gene combinations in
  a population

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• Diploid - term used to refer to a cell that
  contains both sets of homologous chromosomes
• Haploid - term used to refer to a cell that
  contains only a single set of chromosomes and
  therefore only a single set of genes

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Chromosomes

• Humans have 46 chromosomes
• 23 from your mothers egg
• 23 from your fathers sperm
• A normal human cell is a diploid cell (2N)
• A sex cell or gamete (egg or sperm) is a haploid
  cell (N)
• In human cells what does N represent?
• 23

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Apply what we learned about human cells to
drosophila melanogaster.

• Does 2N or N represent this cell best?
• Is this cell haploid or diploid?
• What number does N represent?

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• Homologous - term used to refer to chromosomes
  that each have a corresponding chromosome from
  the opposite-sex parent
• Homologous chromosomes are similar in shape,
  position and information, but not identical to
  each other.

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Meiosis

• Meiosis is a process of reduction division in
  which the number of chromosomes per cell is cut
  in half through the separation of homologous
  chromosomes in a diploid cell.
• Tetrad - structure containing 4 chromatids that
  forms during meiosis.
• crossing-over - process in which homologous
  chromosomes exchange portions of their chromatids
  during meiosis

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• Formation of a tetrad while going through the
  process of crossing-over
• This occurs during prophase I of meiosis

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Meiosis is broken down into two halves. Meiosis I
an Meiosis II
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Meiosis II
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Gamete Formation

• Meiosis produces four genetically different
  haploid cells.

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Comparing Mitosis and Meiosis

• Similar processes with very different and
  distinct outcomes
• Mitosis results in the production of two
  genetically identical diploid cells (2N), whereas
  meiosis produces four genetically different
  haploid cells (N).