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.

5 Replies 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

  2. Enlightening article! Read up to M.Sc. in Zoology. But I did not know that the XX and XY combination can be different also. This should be taught in schools and colleges also.

  3. Has the videocast become available on “Sex-Biased Genome Evolution,” dated 10 a.m. ET on April 10, 2019?
    Thank you.

Comments are closed.