Red-green color blindness is a human x-linked recessive disorder. the normal allele, xb, is dominant to the mutant allele, xb. jill has normal color vision, but her father is color blind. jill marries tom, who also has normal color vision. jill and tom have a daughter who has turner syndrome and is color blind. how and from whom did the daughter inherit color blindness?

Very interesting problem!

On first reading, it sounded impossible.  Tom has normal vision, and there are no male carriers for x-linked recessive disorders.  So the daughter can at best (or worst) be carrier of the disorder.

We are told that the daughter has the disorder, but the daughter can only be a carrier with genotype XBXb.

We are also told that Turner Syndrome, which is a disorder related to the x-chromosome.  Half of those affected have one of the x-chromosomes missing (monosomy), and some others have some cells with missing or deformed x-chromosomes (mosaicism).  Under these circumstances where the normal chromosome is missing, the X-linked recessive Xb allele will be expressed, hence even a carrier can express the red-green colour-blindness.

From the pedigree chart, we can deduce that the colour-blindness must be inherited from Jill, the mother.  Tom with normal vision cannot be a carrier because X-linked recessive disorders do not have male carriers.

The daughter's colour-blindness is derived from two sources,
1. inherited Xb allele from mother Jill
2. Turner syndrome that allowed the single allele to express colour-blindness.

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.