Question

What induces the completion of meiotic division in secondary oocytes? Name the resultant cells formed.

Answer 1

Hint: The secondary oocyte is the cell that is developed by meiosis I in oogenesis. The secondary oocyte endures a second meiotic division and generates a single haploid ovum and the second polar body. Thus, a single secondary oocyte results in a single egg.

Complete step-by-step anwer:
Fertilisation of an egg by a sperm normally takes place in a Fallopian tube, most frequently in the part of the tube which passes above the ovary. For fertilisation, sperm must “swim” from the vagina in which they are deposited, through the cervical canal to the uterus, and then across the body of the uterus to one of the Fallopian tubes. As soon as the sperm enters a Fallopian tube, tubular fluids carry them through the tube toward the secondary oocyte at the other end. The secondary oocyte is generated by meiosis I in the primary oocyte. It begins the second meiotic division immediately but gets arrested at metaphase.
Meiosis completes only at the time of fertilisation as soon as the sperm enters the ovum. The entry of sperm through the zona pellucida layer induces the completion of meiosis in the secondary oocyte. If the secondary oocyte is fertilised by a sperm as it passes through the Fallopian tube, the secondary oocyte rapidly completes meiosis II, which forms a diploid zygote and another polar body. Then the zygote enters through the fallopian tube to the uterus, during which it endures several mitotic cell divisions. When it reaches the uterus up to five days after fertilisation, it is composed of a ball of cells known as a blastocyst. Within another day or two, the blastocyst transplants itself in the endometrium lining the uterus, and gestation starts.

Therefore the correct answer is Option C.

Note: The secondary oocyte also promote fertilisation. It releases molecules that direct sperm and allows the surface of the egg to fix the surface of the sperm. Then the egg can absorb the sperm, which allows for fertilisation to take place.