Romanovs and Revolution

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Romanovs and Revolution

• A Genetic History Mystery

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The Romanovs
Tsar Nicholas II
Alexandra
Olga
Tatiana
Alexei
Marie
Anastasia
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Grigory Rasputin
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Hemophilia

• Caused by a single, recessive allele.
• This allele codes for a blood-clotting protein.
  If the protein is defective, then the blood does
  not clot properly.
• Untreated, victims often die in childhood or teen
  years, rarely live to adulthood.

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The Windsor Pedigree
This pedigree shows who had hemophilia in the
Windsor family line. Why only males? And who are
the carriers?
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The Completed Pedigree
Notice only women can be carriers. Why? And
heres the real mystery Why are there no
carriers before Victoria?
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Sex-linkage

• Sex-linked traits are carried on the sex
  chromosomes (X or Y). Women have two X
  chromosomes, while men have an X and a Y.
• Most sex-linked traits that have been studied
  well are X-linked. Women need two copies of a
  recessive X-linked trait to show the trait. Men
  only need one.

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How X-linkage works

• Only women can be carriers of X-linked traits,
  since they have two X chromosomes.
• Men can pass an X or a Y to their children. Women
  only have an X.

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Red-Green Color Blindness - X-linked

• If your vision is normal, these should read A
  29, B 45, C abstract, D 26.
• If you are red-green color blind, they might
  read A 70, B nothing, C 5, D nothing.

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Color-blindness Inheritance

• If I have a brother who is red-green color blind
  (which I do), where did he get the color-blind
  gene from? Mom or Dad?
• What are the odds that I am a carrier?

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Things to Remember

• When doing Punnett squares for X-linked traits,
  we track not just the alleles, but the
  chromosomes they are carried on.
• This is only for traits on the sex chromosomes,
  not for traits on the other(somatic) chromosomes.