Irene Ayako Uchida

Genetics

World-famous Down syndrome researcher

"Do your best no matter what you do even if it's a menial job."

Cytogenetics is the study of chromosomes in cells. It concentrates on the behaviour and identification of chromosomes. By knowing the state of the chromosomes and especially the genes within them, scientists can now predict many genetic disorders. Uchida was the first person to bring this technique to Canada. One of the many practical applications of cytogenetics is the ability to diagnose genetic diseases in fetuses, thus preparing many pregnant mothers and their spouses for the birth of an abnormal child, or giving them the choice of terminating the pregnancy.

Human chromosomes. Click to enlarge.

1. In humans, 23 pairs of chromosomes have tens of thousands of genes that carry the information needed to create a unique person. For each pair, one comes from the father, the other from the mother. The bands indicate different types of DNA (DeoxyriboNucleic Acid—the molecule that contains genetic information). Cytogeneticists use the bands to help match the pairs.

2. These are the chromosomes of Jodi Kaczur, a Special Olympics champion and actor, who happens to have Down syndrome. You can tell by Jodi’s two X chromosomes that she is a girl. Boys have one X and one Y chromosome.

3. Down syndrome is caused by the accidental tripling of chromosome number 21 during conception. It was first described by the English physician John Langdon Down in 1866. Other genetic diseases are caused by tripling of chromosomes number 13 or 18. The tripling is called trisomy. People with trisomy of chromosomes 13 or 18 usually die as fetuses, and are miscarried. Those who are born alive do not usually live more than a year. The incidence of Down syndrome is related to the age of the pregnant woman. Women under 30 have a 1 in 1,200 chance of having a Down syndrome baby. By age 35 the chance is about 1 in 500 and by age 45 about 1 in 25.

4. Jodi with actor Arnold Schwarzenegger. People with Down syndrome are not as different as you might think. According to Uchida, who has known hundreds of them, “They are often very happy and affectionate.” Yet like everyone else, they have unique personalities with strengths, weaknesses, interests, dreams and ideas. New education and training programs are helping Down syndrome people live happy productive lives. Unfortunately, because of health problems arising from their genetic disorder, only a few live beyond their mid fifties.


ACTIVITY

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MYSTERY

Uchida believes geneticists may be able to find out how to deactivate one of the chromosomes in an individual with trisomy. This happens naturally during the embryonic development of all women — one of their X chromosomes is always deactivated. If geneticists can find a technique to deactivate certain chromosomes such as the extra ones at numbers 21, 13 or 18, the related genetic conditions may be cured at an early embryonic stage.

Explore Further

Jason Kingsley and Mitchell Levitz, Count Us In: Growing Up with Down Syndrome, Harvest/HBJ Books, 1994.

Library and Archives Canada has a webpage about Uchida.

The Canadian Down Syndrome Society is a good source for more information.

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