Introduction to Genetics

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Introduction to Genetics

• SBI3U _at_ RHSA

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Genetics

• Genetics studies how genetic information about
  traits is passed from generation to generation.

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Ms. Murrays Great-grandparents
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Inheritance

• In sexually reproducing organisms the inheritance
  of traits determines genetic variation among
  offspring.

• Genetic variation is required for evolution.

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Chromosomes made of DNA

• Chromosomes are coiled DNA inside the nucleus of
  a cell.
• Each chromosome carries the genetic information
  for a specific set of traits.

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Genes

• A gene is a short segment of DNA that controls
  the expression of a trait.
• A gene has instructions to make one protein.

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Traits

• Some traits like lactose tolerance, are
  controlled by one gene.
• Other traits, like body shape, are controlled by
  many genes together.

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Structure of DNA

• The structure of DNA is identical in all plants
  and animals, strong evidence supporting evolution
• DNA has a double helix shape.

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Somatic cells

• Somatic or body cells all have 46 chromosomes or
  23 pairs of chromosomes.
• Somatic cells are diploid and contain 2 copies of
  each chromosome.
• Somatic cells are produced by mitosis.

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Sex cells (egg or sperm)

• Gametes or sex cells are only found in the
  ovaries or testes of humans.
• There are 23 chromosomes in a human egg or sperm
  cell.
• Gametes are haploid and have a single copy of
  each chromosome.
• Sex cells are produced by meiosis.