Some causes could be the mother smoking, drinking, doing drugs etc. Or even simply her body doesn’t fully accept the baby growing inside her so it acts out against it. Sounds strange but it happens. Also if the mother is sick with Zika or another virus, it can harm the baby’s growth.
I think you're talking about histones. Histones are proteins found in eukayotic cell nuclei. Histones are what DNA wrap around so it fits inside the nucleus and helps with the formation of chromosomes.
Esa canción la conozco jaja
Endocrine and circulatory (C) Endocrine system consists of glands and the hormones they secrete whist the circulatory system is the blood or as I like to call the “transport system” of the body.
Mitochondria is the main power house
Hope this helped :))
