Biology Now, 2e

136 ■ CHAPTER 08 Chromosomes and Human Genetics

GENETICS

in Germany, holding tightly to the hope that he

might be able to save Felix’s life. Klein, a pedia-

trician who has made a career of studying rare

diseases, was running a clinical trial testing

a new treatment for WAS. The treatment was

risky and the results unknown, but it was Felix’s

only hope to be cured of his deadly disease—

one that had perplexed scientists for decades.

A Mysterious

Malady

More than 70 years earlier, in 1937, three young

brothers had come to see Dr. Alfred Wiskott, also

a German pediatrician. At first, Wiskott had no

idea what was causing their symptoms. The boys

bled abnormally: their blood was unable to clot,

and they had bloody diarrhea. They also had

recurring ear infections and blistering, weep-

ing rashes on their skin. Wiskott recorded their

symptoms, but he could not help the boys. All

three died at a young age.

What had killed the brothers? Their parents

also had four daughters, all of whom were healthy,

so it was unlikely that an infection, a toxin, or

an environmental factor had caused the illness.

Instead, Wiskott suspected, the boys might have

inherited a disease from their parents.

Thanks to the chromosome theory of inheri-

tance, Wiskott knew that the boys had inherited

hereditary material, in the form of chromo-

somes, from their parents. Recall from Chapter 7

that offspring inherit one chromosome from

the mother and one from the father. Wiskott

suspected that a gene on one of the inherited

chromosomes was causing the mysterious illness.

A disease caused by an inherited mutation,

passed down from a parent to a child, is a genetic

disorder. Wiskott recognized the importance of

researching genetic disorders, since such studies

could lead to the prevention of or cure for a disease.

But daunting problems have long plagued the

study of human genetic disorders. From a biolog-

ical point of view, humans have a long generation

time, select their own mates, and decide whether

and when to have children. In addition, human

families tend to be much smaller than would be

ideal for a scientific study. From an ethical point of

view, geneticists and physicians cannot intervene

and perform experiments directly on humans to

determine how genetic disorders are inherited.

F

elix clutches his mother’s side. Her arm

is wrapped tightly around him. Lying in

a rumpled white hospital bed, Felix looks

away from the two red tubes protruding from

his body. Blood pumps out one side of his body

into a humming machine next to the bed and is

pumped back into the other side. Dr. Christoph

Klein steps into the room, clothed head to toe in

blue scrubs, and offers a smile and a reassuring

word (Figure 8.1).

Shortly after his birth in 2005, Felix began

to bleed. His parents rushed him to an intensive

care unit. The bleeding eventually stopped, but

the hospital visits did not. Three years later, Felix

was diagnosed with a rare and deadly disease:

Wiskott-Aldrich syndrome (WAS). “Wiskott-

Aldrich was the very last diagnosis I would ever

want to receive,” Felix’s mother later said. “Every

day I prayed, ‘Please, Lord, let this chalice pass

from us.’”

Felix’s pediatrician feared the worst. WAS

patients suffer from recurring infections, pneu-

monia, bleeding, and rashes; they often develop

leukemia or lymphoma and die of complications

due to infections. Some patients can be treated

with a bone marrow transplant. However, if the

donor is not a matched sibling or a close unre-

lated match, survival rates are low.

So, in 2009, Felix’s family appeared in

Klein’s office at the Hannover Medical School

Figure 8.1

Felix and Dr. Klein

Dr. Christoph Klein examines Felix, who suffers from a rare genetic disease.