Roughly, what percentage of DNA
bases are the same across all humans? (A) Zero percent, (B) less than 25
percent, (C) 50 percent, (D) 75 percent, (E) greater than 99 percent.
DNA, or deoxyribonucleic acid, is
the molecule that carries genetic information in all living organisms. A molecule of DNA is most commonly
composed of two strands, each of which is a chain of individual units called
nucleotides. Each nucleotide in DNA contains a
nitrogenous base, which can be either guanine, cytosine, adenine, or thymine. We can see these different
nucleotides here and the corresponding nucleotide sequence for one of these DNA
strands as it coils around the opposing strand.
In humans, if we look at the
complete sequence of DNA, or our genome, it’s over three billion nucleotides
long. We discovered this after sequencing
the human genome as a part of the Human Genome Project. This was a worldwide effort by
multiple scientists that took over 10 years to complete. When comparing the genome sequence
between humans, we find that we share over 99 percent of our DNA with each
Getting back to our question, the
option that correctly identifies the percentage of DNA bases that are the same
between humans is given by answer choice (E): greater than 99 percent.