romanovs and revolution a genetic history mystery

Romanovs and Revolution

Romanovs and Revolution

A Genetic History MysteryA Genetic History Mystery

Tsar Nicholas IITsar Nicholas II

AlexandraAlexandraOlgaOlga

TatianaTatiana

MarieMarie AnastasiaAnastasia

AlexeiAlexei

The RomanovsThe Romanovs

The Romanov children

The Romanov children

Tsarevich AlexeiTsarevich Alexei

Grigory RasputinGrigory Rasputin

HemophiliaHemophilia

•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.

•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.

The Windsor PedigreeThe Windsor Pedigree

This pedigree shows who had hemophilia in the Windsor family line. Why only males? And who are the carriers?

This pedigree shows who had hemophilia in the Windsor family line. Why only males? And who are the carriers?

The Completed PedigreeThe Completed Pedigree

Notice only women can be carriers. Why?And here’s the real mystery:

Why are there no carriers before Victoria?

Notice only women can be carriers. Why?And here’s the real mystery:

Why are there no carriers before Victoria?

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.

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.

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.

Color-blindness InheritanceColor-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?

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.