X Chromosome Inactivation

0:00 Tortoiseshell cats as a model for studying X-chromosome inactivation (XCI)
0:22 Genetic basis of pigmentation: orange gene alleles on the X
1:11 Early development: cell division, random XCI (heterochromatin; Barr body)
2:40 Pressure for the evolution of XCI: sex chromosome dosage between the sexes
3:50 Mosaic phenotypes result from random XCI
5:56 A practical use for the mosaic phenotype