In three to five sentences, explain why sickle cell disease became so prevalent in certain east african populations.

Why do you think the puppy litter was all dark-haired?

This is one of the five kingdoms in the older biological succession. organisms in this kingdom are prokaryotic.

Imagine a self-reactive t cell that has not undergone clonal deletion in the thymus (that is to say, it has escaped central tolerance). if it encounters self antigen in the absence of an infection or inflammation, what will happen to this self-reactive t cell? (select two answers) (a) the t cell undergoes clonal expansion. (b) the t cell gains effector functions. (c) the t cell undergoes apoptosis. (d) the t cell becomes activated. (e) the t cell becomes anergic.