The Human Genome Project found that
the genomes of humans are very similar. Roughly, what percent of the human
genome is shared between humans? (A) 80 percent, (B) 88 percent, (C)
greater than 99 percent, (D) 75 percent, or (E) 50 percent.
This question is asking us about
how similar our genomes are. So what is a genome exactly? Our body is made up of cells. Most of these cells contain a
nucleus that contains DNA. DNA is a special molecule that
gives the cells the instructions it needs to grow. It also gives us different traits
and is why some of us are taller and is why some of us have blue eyes, while others
have green eyes. These traits are given by sections
of DNA that we call genes.
If we unravel this DNA a little bit
and look at it more closely, we can see that there’s different sections of DNA that
we call genes that code for different traits. So this gene here might code for
the trait that makes this person tall, and this one here might code for the eye
color trait. If we unravel this DNA even
further, you’ll notice the double-helix-shaped structure and these different colored
boxes. These are called base pairs and are
special chemicals that are like a kind of alphabet. There’s guanine or G for short,
cytosine, adenine, and thymine. These base pairs give the
instructions needed for our different traits.
Here’s a short sequence of DNA,
which is made up of one, two, three, four, five, six base pairs. Different genes have different
lengths with unique sequences of these base pairs to code for specific traits. The Human Genome Project was a
worldwide project that aimed to determine the sequence of all the base pairs in
human DNA. A genome is the complete set of DNA
of an organism. In humans, the sequence of our
genome is about three billion base pairs long.
Once we had the complete sequence
of our DNA, we could then start comparing this sequence between humans. We found that our genomes were
about 99.9 percent the same. So even a stranger, who you are not
related to, shares more than 99 percent of their DNA with you. Therefore, more than 99 percent of
our genome is shared between humans.