It has been well documented that women above 40 have an increasing chance of giving birth to babies with Down syndrome. Why is this so?
A) Egg development starts at the fetal stage of women.
B) Eggs are in meiosis I at that time of fertilization.
C) The egg doesn't complete division (meiosis II) until fertilization.
D) The cellular machinery is unable to separate the chromosomes and chromatids, resulting in gametes with abnormal chromosome numbers.
E) All the above are true.

Question

Quizplus · Accepted Answer

All the options provided are true and contribute to the increased risk of Down syndrome in babies born to women over 40. A) Egg development indeed starts at the fetal stage in women, meaning that the eggs are as old as the woman herself. B) Eggs are arrested in meiosis I until the time of fertilization. C) The egg doesn't complete division (meiosis II) until after fertilization occurs. D) As women age, the cellular machinery that separates chromosomes and chromatids during meiosis can become less efficient, leading to an increased risk of gametes with abnormal chromosome numbers, such as the trisomy 21 characteristic of Down syndrome.

It Has Been Well Documented That Women Above 40 Have