Tracing Similarities And Differences In
Our DNA
What percent of their genes match yours?
| Another human? |
100% - All humans have the same genes, but some
of these genes contain sequence differences that make each
person unique. |
| A chimpanzee? |
98% - Chimpanzees are the closest living species to humans. |
| A mouse? |
92% - All mammals are quite similar genetically. |
| A fruit fly? |
44% - Studies of fruit flies have shown how shared genes govern
the growth and structure of both insects and mammals. |
| Yeast? |
26% - Yeasts are single-celled organisms, but they have many
housekeeping genes that are the same as the genes in humans,
such as those that enable energy to be derived from the breakdown
of sugars. |
| A weed (thale cress)? |
18% - Plants have many metabolic differences from humans.
For example, they use sunlight to convert carbon dioxide gas
to sugars. But they also have similarities in their housekeeping
genes. |
Why Were Genes Used In This Comparison, and How Do They Relate
To DNA?
Genes are the fundamental units of DNA function. In DNA terms,
genes are discrete sections of the DNA sequence that are part of
much longer DNA molecules. They provide the biochemical instructions
for producing all of the components of biological organisms. Some
genes specify visible physical traits, while others govern metabolic
processes. Most traits, such as the shape of your face, require
the actions of many genes.
Why Are We So Similar?
The DNA of these species is so similar because the basic organization
of life is widely shared, with the largest differences found between
plants and animals, or between tiny single-celled organisms like
yeast and large multicellular organisms like ourselves. The similarities
reflect a common ancestry that appears to be shared by all life
on Earth.
Are People Really Identical?
Even though humans share 100% of the same genes, the instructions
contained within the genes are not entirely identical. Each person
is unique. People have different hair colors, facial structures,
and other traits. These differences between individuals result
from very small differences in their DNA sequences. DNA also contains
many so-called "housekeeping genes" that control important
metabolic processes. As you will see, some of the differences in
these genes can cause illness.
Although the DNA of any two people on Earth is, in fact, 99.9%
identical, even a tiny difference can have a big effect if this
difference is located in a critical gene.
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