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happen for many reasons and are almost always unpredictable— hence the sometimes weird nature of evolution. Take the duckbilled platypus as an example—the mutations that produced that animal’s unique appearance were random, but they have worked for that particular animal and have helped the species continue to exist for millions of years. Like genes, genetic disorders are split into dominant and recessive problems. A dominant genetic disorder occurs when the mutation occurs to a dominant gene. For example, a family’s dominant gene for brown eyes may mutate to cause a person to have two different colored eyes. When such a mutation occurs on a dominant gene, every child a parent produces has a 50 percent chance of also having that same genetic disorder.

Segments of DNA that carry specific coded information are called genes. The specific genes for a particular trait are always found in the same place on a DNA strand.

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Understanding Genetics