since homocysteine is derived entirely from methionine , methionine deficiency will cause intracellular folate deficiency , and the rate of mitosis of rapidly dividing cells will be reduced . although these two processes have evolved as a response to methionine deficiency , they also occur in b12 deficiency , which the cell mistakenly interprets as lack of methionine . the resulting response is inappropriate and gives rise to a potentially lethal anaemia .
C0026255
mitosis
C0007634
cell