Human Genetics

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Human Genetics

• How we study this stuff in humans

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Pedigrees

• Human genetics are studied using PEDIGREES, which
  diagram how a trait is inherited in a family. A
  pedigree helps us determine genotypes of the
  family members

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Pedigrees

• Also called a family tree
• Squares represent males and circles represent
  females
• Horizontal lines connecting a male and female
  represent mating
• Vertical lines extending downward from a couple
  represent their children
• A shaded symbol means the individual possess the
  trait
• Half-shaded symbols are carriers

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Pedigrees

• A pedigree for the recessive allele that causes
  albinism.
• Albinos are humans that have no pigment, their
  skin is very pale and all their hair is white,
  including eyebrows and eyelashes.
• This pedigree shows how albinism can be inherited
  over 2 generations.

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• Other animals can also be albinos, like this
  deer.

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Human Genetic Diseases

• Albinism - inability to produce pigment, white
  hair and skin, autosomal recessive
• Huntingtons - symptoms of mental illness appear
  late in life, autosomal dominant
• Sickle Cell Disease - blood cells shaped
  abnormally, autosomal recessive
• Tay Sachs - fat builds up in the brain of infants
  causes degeneration and early death, autosomal
  recessive
• Hemophilia - bleeder's disease, inability of the
  blood to clot, sex linked recessive
• Cystic Fibrosis - mucus builds up in lungs
  causing respiratory problems, autosomal recessive

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Twins

• Human genetics can also be studied by looking at
  IDENTICAL TWINS, which help establish whether
  NATURE or NURTURE influences are traits.
• This is because identical twins should have an
  identical genes (Nature)!

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Twin Studies

• Modern twin studies have shown personal traits to
  be partially influenced by one's genes, with some
  characteristics showing a strong influence (e.g.,
  homosexuality, IQ).
• Identical twins (should) have identical DNA.
  They are represented as monozygotic (MZ) meaning
  they come from one egg.
• Fraternal twins arent any more related than a
  brother or sister and are represented as
  dizygotic (DZ). They come from two eggs.

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• Twin concordances for seven psychological traits
  (sample size shown inside bars).

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Whats to come

• We will finish off talking about genetics by
  focusing on chromosome, gene location, mutations,
  etc.
• Then its on to Embryology, Anatomy, and
  physiology!

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Birth of Modern Genetics

• T.H. Morgan and the discovery of Mutations and
  Chromosomes

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Rediscovering Mendel

• In 1900 several scientists across Europe came to
  the same realization about heredity that Mendel
  had some 40 years before. But they arrived at the
  discovery from a very different direction.

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Thomas Hunt Morgan

• No one could say for sure what mutations did
  until they could be studied up close. That became
  possible in the laboratory of a Columbia
  University biologist, Thomas Hunt Morgan.

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Lords of the Fly

• Morgan bred fruit flies by the thousands, and his
  team tried to create mutant flies with x-rays,
  acids, and other toxic substances.
• Finally, in one lineage of flies, the researchers
  found a surprise. Every single fly in that line
  had been born with red eyes, until one day a fly
  emerged white eyes. Something had spontaneously
  changed in the white-eyed fly.

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Fly Mutations

• Can you find the White eyed fly?

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• Through the work of Morgan (and his grad
  students) it was discovered that genes are found
  on chromosomes.
• This led, years later, to the discovery of DNA
  and its structure by Watson and Crick!