OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What event marks the beginning of the menstrual cycle?

1. The release of an egg

2. The thickening of the uterus lining

3. The start of menstruation

4. The production of progesterone

The correct answer is: The start of menstruation

The beginning of the menstrual cycle is marked by the start of menstruation. Menstruation refers to the shedding of the uterine lining that occurs when there is no fertilization of an egg. This event signifies the end of one cycle and the beginning of another, triggering a new set of hormonal changes that will eventually lead to ovulation and the preparation of the uterus for a potential pregnancy. The other choices represent different phases or events within the menstrual cycle. For example, the release of an egg happens during ovulation, which occurs about midway through the cycle, after the initial phase of menstruation. The thickening of the uterus lining happens in preparation for potential implantation following ovulation. Similarly, the production of progesterone occurs primarily after ovulation, when the corpus luteum forms and produces this hormone to maintain the uterine lining for a possible pregnancy. Thus, while all these events are integral to the menstrual cycle, they occur after menstruation has started the cycle anew.