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

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.

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:

• a) In infancy, because it’s unclear whether the baby is a girl or boy

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

• b) At puberty, because sexual development doesn’t progress as expected

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

• c) During child-bearing years, because the person is infertile or has reduced fertility

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

• d) At any time during a person’s life

  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?

• a) A woman with a missing X chromosome (X0)

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

• b) A man with a missing X chromosome (0Y)

  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.

• c) An extra X chromosome (XXY)

  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.

• d) An extra Y chromosome (XYY)

  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…

• a) Hemophilia A

  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.

• b) Duchenne muscular dystrophy

  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.

• c) Down syndrome

  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.

• d) Red-green color blindness

  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?

• a) The original sex chromosomes were both as large as today’s X chromosome. Over time, the Y chromosome lost genes and shrunk.

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

• b) The original sex chromosomes were both as large as today’s Y chromosome. Two Y chromosomes got attached and were passed down that way, resulting in the larger X chromosome today.

  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.

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