Chromosomally speaking, what do you know about sex? Take a quiz to find out.

Floating letters X and Y to represent chromosomes, coming together to form chromosome configurations XX and XY against a background of rotating double helixes.

Women have two X chromosomes (XX) and men have one X and one Y (XY), right? Not always, as you’ll learn from the quiz below. Men can be XX and women can be XY. And many other combinations of X and Y are possible.

NIGMS Director’s
Early-Career Investigator Lecture

Sex-Biased Genome Evolution

Profile photo of Melissa Wilson outside with red scarf, wearing glasses and smiling.

Melissa A. Wilson, Ph.D.
Arizona State University

Wednesday, April 10, 2019
10:00-11:30 a.m. ET

Lecture followed by Q&A session
Info on the ECI Lecture webpage

You can learn more by listening to the live stream of a talk, titled “Sex-Biased Genome Evolution,” at 10 a.m. ET on April 10. The speaker, Melissa A. Wilson, is a researcher at Arizona State University who uses high-performance computing, statistics, and comparative genomics to study the X and Y chromosomes.

Wilson’s 30-minute talk is geared for an undergraduate-level audience and will be followed by a Q&A session. We encourage you use the hashtag #ECILecture to live-tweet the event and submit questions during the Q&A session.

For more details about Wilson’s work, background, and upcoming event, visit our ECI Lecture webpage. A videocast of the talk will be available to view live and at a later date.

Until then, see how well you do on the quiz below.

    1.) Conditions that result from an atypical number of sex chromosomes are frequently diagnosed:

  • That’s the case for some people, but many others have normal sexual organs. Try a different answer.

  • This can happen, but it doesn’t always. Puberty can progress normally. Consider other answers.

  • True in some cases, but it’s not the best answer. Try again.

  • That’s it! The symptoms and severity of these conditions vary widely and are not always recognized. About a million people in the U.S. are estimated to have a sex chromosome number that’s atypical. Some people with these conditions don’t even know it!

    2.) Which of the following chromosomal configurations is never possible?

  • Nope. Women with only one X chromosome (X0) have Turner syndrome. Give it another shot.

  • You’re right! This genotype is fatal long before birth. The X chromosome contains many genes that are essential to life for both males and females.

  • Actually, this is more common than you might think. It’s known as Klinefelter syndrome. It affects between 1 in 500 to 1,000 newborn males. Try again.

  • Sorry, wrong answer. The XYY genotype is estimated to occur in approximately 1 in 1,000 newborn boys.

    3.) All of the following are sex-linked conditions except…

  • Hemophilia A, a blood-clotting disorder, is caused by alterations to a gene on the X chromosome. In most cases, boys inherit the condition from their mothers, who carry the altered gene but do not experience symptoms (typically, women are protected because they carry a fully functional version of the gene on their second X chromosome). In about 30 percent of cases, a spontaneous genetic change causes the condition.

  • Duchenne muscular dystrophy is caused by an alteration of the dystrophin gene on the X chromosome. The condition, characterized by progressive muscle degeneration and weakness, is usually diagnosed during early childhood. Like most X-linked recessive traits, it primarily affects boys. Women act as carriers who pass the altered gene to their children.

  • You got it. Down syndrome, also called trisomy 21, results from an extra chromosome 21. All the other conditions are caused by genetic variations on the X chromosome.

  • Red-green color blindness affects up to 8 percent of men and 0.5 percent of women of northern European descent. The genes responsible for the most common, inherited color blindness are on the X chromosome. Women who have unaffected genes on their other X chromosome will not experience color blindness but can pass the altered genes to their children.

    4.) Today, the X chromosome in humans is much larger than the Y chromosome. Millions of years ago, these two sex chromosomes were the same size. What happened?

  • Yes, it’s true. Melissa Wilson will explain more in her April 10 talk. Join us by videocast live or later.

  • Although sometimes chromosomes (or parts of chromosomes) can stick to each other, that’s not what happened in the case of X and Y. Melissa Wilson will explain more in her April 10 talk. Join us by videocast live or later.


One Reply to “Chromosomally speaking, what do you know about sex? Take a quiz to find out.”

  1. Dear Dr Wilson , I am looking forward for your talk on Sex Chromosomes. Congratulations no better times : Just at the tip of the pyramid on evolution in Sciences information , further at the exordium and the opening of “genes home” door , which is not no other than the chromosomes , will lead to unravel dualities on the beauty of sharing similarities and the uniqueness of the individualidad as a human being . Arnold Vera, MD., MSc.,CDE.,FACE

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