The markings of baby zebras are determined by the color of their skin and hair, which in turn is determined by some genes that control melanin.
Melanin is a substance that gives color to hair, skin, and eyes, and it comes in two types, one is black and is called melanin, and the other is brown and is called tyrosinase.
There are two types of melanin in the hair of baby zebras, one is black and the other is white. Black melanin is produced by a type of cell called melanocytes, which transport melanin to the roots of the hair. White melanin is produced by a type of cell called alovonia, which inhibits the production and transport of melanin.
The markings of baby zebras are formed during their embryonic development, a process that takes about 12 months. During this process, melanocytes and leukocytes migrate from the embryonic neural crest (a primitive type of nerve tissue) to different levels of the skin, forming different markings. This process is influenced by both genes and the environment, such as temperature, humidity, light, etc. These factors can affect the expression of genes and thus the formation of markings.
Generally speaking, baby zebras will first have black stripes on their backs, then white stripes on their abdomen, and finally black and white stripes on their limbs and head. This order is determined by the interaction of genes and the environment, and the specific mechanism is not well understood. There is a hypothesis that the markings of small zebras are controlled by a signaling molecule called Wnt, which can affect the differentiation and migration of melanocytes. The concentration of Wnt varies in different parts of the embryo, resulting in a different order of markings.
However, because the black and white stripes appear first on the legs, it is particularly noticeable.