Multiple choice

Why would you predict that half of the human babies born will be males and half will be females?

  1. Because of the segregation of the X and Y chromosomes during male meiosis

  2. Because of the segregation of the X chromosomes during female meiosis

  3. Because all eggs contain an X chromosome

  4. Because, on average, one-half of all eggs produce females
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The equal sex ratio at birth occurs because during male meiosis, X and Y chromosomes segregate randomly into different sperm cells. Each sperm carries either X or Y, and fertilization of an X-bearing egg is equally likely with either type. Egg cells always contain X chromosomes, so they don't determine sex - the sperm does.

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