Diploid cells

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Diploid cells

• A cell with two of each kind of chromosome

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Haploid

• A cell with one of each kind of chromosome
• Example Gametes

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Homologous Chromosomes

• Paired chromosomes with genes for the same trait

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Haploid

• A cell with one of each kind of chromosome
• Example Gametes

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Tetrad

• Two homologous chromosomes each made up of two
  sister chromatids.

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Crossing over

• Chromosomes exchanging genetic material
• Creating new combinations of alleles
• Resulting in genetic variation

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Why meiosis?

• To produce gametes with half the number of
  chromosomes as other cells (somatic cells)

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Why meiosis?

• Haploid Gametes combine to make one diploid cell
  which goes through mitosis for growth and
  development

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Mistakes in meiosis

• Non- disjunction

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Non Disjunction

• The failure of homologous chromosomes to separate
  properly during meiosis

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Trisomy

• One form of non-disjunction where one gamete has
  an extra chromosome
• Downs syndrome is an example

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Monosomy

• Gamete is missing a chromosome
• Most zygotes do not survive

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Triploidy

• Gamete has an entire extra set of chromosomes
• Very rare in animals