Humans and large primates have smiliar DNA through evolution

You wanted to know

A young patron from the Grayslake Area Public Library asked, "Why is our DNA so similar to orangutans?"

DNA - deoxyribonucleic acid - is found in nearly all living organisms. It's the instruction guide that tells cells what kind of cells they are supposed to be and how they are supposed to function.

DNA contains operating instructions for each part of an organism - organs, nerves, muscles and bone - and for all metabolic processes. DNA contains information that is passed from parent to child that defines traits such as hair color, eye color and height.

Every cell has DNA, and genes are a part of DNA. There are trillions of cells in a human body and each strand of DNA contains 22,000 genes.

All humans have 100 percent of the genes to be a human.

"Humans are very similar to large primates like chimps, bonobos and orangutans," explained Dr. Barbara Burton, professor of pediatrics in the department of genetics, birth defects and metabolism at the Ann & Robert H. Lurie Children's Hospital of Chicago. "We are similar because we all evolved from a common ancestor."

Since most living organisms have DNA, there are similarities across organisms. Weeds have 18 percent similarity to humans according to the website "Putting DNA to Work." A mouse has 92 percent similarity, and chimps have 98 percent of the same DNA as humans.

Because researchers have identified DNA and decoded the very long strings of genes on a DNA strand, they've been able to understand how to recognize and treat illnesses that can occur when genes don't operate according to plan.

"It's a revolutionary way to diagnose illness to access a person's DNA, an ability that's come about in the last 20 years," Burton said.

She offers the example of PKU - an inherited disease that affects one in every 10,000 babies born in the U.S. When the disease is present, a genetic mutation eliminates a necessary enzyme. The missing enzyme causes the body to produce excess levels of phenylalanine, which is toxic to the central nervous system.

Since the 1960s, all newborns in the U.S. have genetic testing for the presence of PKU.

"It used to always cause severe mental retardation. Many people over age 45 with PKU are severely impaired. Now every baby is tested, and with treatment we have children and adults who are normal. We have adults who are lawyers and doctors and who work for the CIA; had it not been for the treatment they would not be functioning today," Burton said.

Each day, Burton and her colleagues test DNA samples to check for disease genes.

"I want to know what gene changes that patient has to see, what's different about that gene," Burton said. "We test the DNA to see if there's a mutation. Sometimes we look at the entire genome, sometimes we perform exome sequencing."

Exome sequencing only looks at about 1 percent of the genome.

Check it out

The Grayslake Area Public Library District suggests these titles on orangutan and DNA:

• "Orangutans," by Susan Kueffner

• "Orangutans," by Deborah Dennard

• "DNA and Heredity," by Casey Rand

• "Genetics: Investigating the Function of Genes and the Science of Heredity," by Trevor Day

• "Genetics: Breaking the Code of Your DNA," by Carla Mooney