A minimal level of intra-tumour heterogeneity is a simple consequence of the imperfection of DNA replication: whenever a cell (normal or cancerous) divides, a few mutations are acquired - leading to a diverse population of cancer cells.
There are two main sources of vitamin A, animal sources and plant sources. Known as retinol, animal sources of this essential vitamin contain preformed vitamin A. Vegetable sources contain carotenoids, such as beta-carotene, which is converted to retinol by the body.lant sources of vitamin A include many fruits and vegetables that have rich, deep, intense color. The more intense the color of the vegetable or fruit, the more beta-carotene it contains. Plant sources of carotenes include: 1  Sweet potatoes. 2  Carrots. 3  Pumpkin. 4  Winter squash. 5  Cantaloupe. 6  Pink Grapefruit.
These are foods that contain vitamin A or its precursor called beta-carotene. Animal foods contain vitamin A whereas no plant food provides vitamin A but instead they have beta-carotene which is converted to vitamin A in the liver.The foods listed in this article are good sources of vitamin A or beta-carotene.ne tablespoon provides 69% of the recommended daily amount of Vitamin A. Itâs also an impressive source of Vitamin C, potassium, and calcium. Serving Size (1 tablespoon), 3448 IU of Vitamin A (69% DV), 20 calories. Mangoes. Mangoes are sweet, juicy fruits that have a place both in main dishes and on dessert plates.