A is the answer
a replication fork
Genes involved in production of abnormal red blood cells may have an abnormal sequence of bases (nucleotides), like inherited alteration in the gene for JAK2, a protein with enzymatic activity that's linked to the abnormal production of blood cells.
An absorptive heterotroph is an organism which secretes enzymes externally into its environment to digest organic materials which are then absorbed.
American black bear, Cougar, Big Horn Sheep and some others.
