Which statement about sex chromosomes in humans is true?

Which statement about sex chromosomes in humans is true?

• A. They are identical in males and females
• B. They determine the sex via autosomes
• C. They pair as X and Z for sex determination
• D. They are X and Y and determine sex

Answer: (D)

Sex is determined by a pair of sex chromosomes in humans. Females have two X chromosomes, while males have one X and one Y. The Y chromosome carries genes, like SRY, that kick off the development of male characteristics, so the presence of Y directs male development. Without Y, the default pathway leads to female development. This is why the statement that sex chromosomes are X and Y and determine sex is true. The other ideas don’t fit because sex isn’t controlled by autosomes, which are the non-sex chromosomes; and humans don’t use a Z chromosome for sex determination. Also, males and females aren’t identical in their sex chromosomes—one has XY, the other XX—so they aren’t the same across sexes.

Sex is determined by a pair of sex chromosomes in humans. Females have two X chromosomes, while males have one X and one Y. The Y chromosome carries genes, like SRY, that kick off the development of male characteristics, so the presence of Y directs male development. Without Y, the default pathway leads to female development. This is why the statement that sex chromosomes are X and Y and determine sex is true.

The other ideas don’t fit because sex isn’t controlled by autosomes, which are the non-sex chromosomes; and humans don’t use a Z chromosome for sex determination. Also, males and females aren’t identical in their sex chromosomes—one has XY, the other XX—so they aren’t the same across sexes.