10. Suppose a target sequence for CRISPR-Cas9 editing is 20 bases long and the haploid genome size is 2.5 billion nucleotides. About how many times would this sequence be expected to appear in the genome at random assuming that all four bases are equally frequent

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.