The Y chromosome does not cause color blindness. Colorblindness is a defective gene on the X chromosome. Females have 2 x chromosomes, thus one can serve as a backup for a defective gene. However, the Y chromosome in males is almost totally defective, thus does not have a backup.olorblindness is a defective gene on the X chromosome. Females have 2 x chromosomes, thus one can serve as a backup for a defective gene. However, the Y chromosome in males is almost totally defective, thus does not have a backup.
Kilwa Kisiwani (also known as Kilwa or Quiloa in Portuguese) is the best known of about 35 medieval trading communities located along the Swahili Coast of Africa.
Lukurmata, located in the Katari valley was the second great city of the Tiwanaku empire. Between 600 and 800 it expanded from 20 hectares to 120 hectares. First established nearly two thousand years ago, it grew to be a major ceremonial center in the Tiwanaku state, a polity that dominated the south-central Andes from 400 to 1200.