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.
Kilwa Kisiwani grew rich and powerful because it was well placed on trading routes between Africa, China, India, and Arabia. Gold, porcelain, quartz, ivory, and other valuable treasures all passed through the island.