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Question Video: Estimating the Percentage of DNA That Is the Same across All Humans Biology

Roughly, what percentage of DNA bases are the same across all humans?


Video Transcript

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 other.

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.

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