A single point mutation<span> can change the whole DNA sequence. Changing one purine or pyrimidine may change the amino acid that the nucleotides code for.</span>Point mutations<span> may arise from spontaneous </span>mutations<span> that </span>occur<span> during DNA replication.</span>
Reptile scales! Or, more specifically, reptiles descended from dinosaurs.
It is the spinal cord that does it.
Negative selection (D) removes the harmful alleles.
