Complex sentence: Cre recombinase is known to be expressed in only a few target cell types and hence the researcher would be typically able to decide where exactly the gene in question is to be knocked out thus allowing for a greater degree of freedom and scientific accuracy.
Split into simpler sentences: Cre recombinase is known to be expressed in only a few cell types. Hence the researcher would be able to decide where exactly the gene in question is to be knocked out, thus allowing for a greater degree of freedom and scientific accuracy.