Crossing over occurs at the four-strand stage when two homologous chromosomes, each consisting of a pair of sister chromatids, are paired. Each crossover involves just two of the four strands and generates two recombinant strands.
Hope this helps!
Unicellular organisms are living things made up of only one cell. For example, bacteria and yeast are unicellular. Multicellular organism are made up of more than one cell. Some examples of a multicellular organisms are humans and animals.
I believe the answer is DNA or Deoxyribo Nucleic Acid
It will work in saliva of animals