Transcript Romanovs and Revolution

Romanovs and
Revolution
A Genetic History Mystery
The Romanovs
Tsar Nicholas II
Alexandra
Tatiana
Marie
Alexei
Anastasia
Olga
The Romanov
children
Tsarevich Alexei
Grigory Rasputin
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.
The Windsor Pedigree
This pedigree shows who had hemophilia in the Windsor
family line. Why only males? And who are the carriers?
The Completed Pedigree
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 Xlinked trait to show the trait. Men
only need one.
How X-linkage works
• Only women can
be carriers of Xlinked 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 redgreen color blind,
they might read:
A = 70, B =
nothing, C = 5, D
= nothing.
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?
Things to Remember
• When doing Punnett squares for Xlinked 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.