Urgent 20pts what role does recombinant dna play in genetic engineering? it ensures that host dna is the site of cleavage. it is responsible for altering an organism's characteristics. it causes the endonuclease to act on dna and rna. it becomes the point of attachment for dna and rna in the nucleus.

Which statements explains what the fossil records indicates? check all that apply. a) earth is 4.5 billion years old b) many organisms have become extinct c) mammals have always existed on earth d) mass extinctions have occurred several times on earth e) the amount of water on earth has decreased over time?