The answer is the nervous system.
Hope this helps!
Dominant' traits will actually disappear faster if they are disadvantageous.
Think about it: if everyone who has even a single copy of a particular allele is at a disadvantage (manifests the phenotype, in this case six fingers), then even single copies are selected against.
In the case of recessive traits, selection occurs only against homozygous carriers, who may be very rare if the allele itself is rare.
A concrete example would be something like Tay-Sachs disease. If the allele that causes this were dominant, every carrier would die before adulthood, and it would occur only as a very rare de novo mutation. But because it is recessive, it persists for now; heterozygous carriers have no disadvantage.
Solution:
People that born with hemophilia lack or have a low amount of a clotting factor.
Coagulation factors are proteins necessary for normal blood clotting.
Coagulation factors are found in blood plasma. These factors act with Thrombocytes to clot blood.
However, hemophilia is not a decrease in Thrombocytes but a decrease in coagulation factors due to genetic causes.
Diagnosis includes screening tests and clotting factor analysis. Screening tests are blood tests that show whether the blood is clotting properly. Clotting factor tests can reveal a deficiency of clotting factors in the blood plasma and determine the level of severity of hemophilia.
As the coagulation factors are in Blood plasma, we can conclude that the correct answer is:
BLOOD PLASMA
