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Question
How many eggs are released by a human ovary in a month? How many eggs do you think would have been released if the mother gave birth to identical twins? Would your answer change if the twins born were fraternal?
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Solution
Each ovary produces several immature eggs, which are connected with groups of other cells known as follicles. In humans, only one egg is usually removed at a time; however, two or more may emerge during the menstrual cycle. The egg emerges from the ovary between the 14th and 16th days of the typically 28-day menstrual cycle. Fertilisation of a single egg results in one zygote (monozygotic) that divides into two embryos, forming identical twins. If the twins were born fraternal, two eggs would be released. Fraternal twins (also known as non-identical twins) are typically formed when two fertilised eggs are implanted in the uterine wall at the same time. The two eggs produce two zygotes; hence, these twins are also known as dizygotic or binovular twins.
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