Which statement correctly distinguishes autosomes from sex chromosomes in humans?

• A. Autosomes are chromosomes 1-22; sex chromosomes are X and Y; females have XX, males XY.
• B. Autosomes determine sex; sex chromosomes do not.
• C. Autosomes are only present in males.
• D. Sex chromosomes are 1-22.

Answer: (A)

The key idea here is how human chromosomes are organized and what they do. Humans have 22 non-sex autosomes, numbered 1 through 22, that are the same in both males and females. The sex chromosomes are X and Y, and they determine an individual’s biological sex: females carry two X chromosomes (XX) and males carry one X and one Y (XY). This distinction is why autosomes are described as the non-sex chromosomes shared by everyone, while sex chromosomes carry the genes that influence sex development and other sex-linked traits. The statement is correct because it accurately states that autosomes are numbered 1–22, sex chromosomes are X and Y, and the typical male and female chromosome complements are XY and XX, respectively. In contrast, it would be wrong to say autosomes determine sex, or that autosomes are only present in males, or that sex chromosomes are 1–22, since those descriptions mix up where sex information is stored and which chromosomes differ between the sexes.