Question

Read the following & arrange them in a sequence
a) Ova
b) Oogonia
c) Primary oocyte
d) Secondary oocyte
e) Grafiian follicle

Answer 1

• During the development of foetus, many oogonia are produced which undergo mitosis and form primary oocytes. These primary oocytes remain arrested at prophase I of meiosis I throughout the childhood.
• Primary oocytes get covered by granulosa cells and form primordial follicles which develop into Graafian follicle.
• Within each developing follicle, a primary oocyte forms egg or ovum.
• Primary oocyte divides by meiosis I to form secondary oocyte and a polar body.
• Hence a mature Graafian follicle contains a secondary oocyte and the first polar body.
• At ovulation secondary oocyte is released from the follicle.
• At fertilisation, the secondary oocyte undergoes meiosis II to form egg or ovum and the second polar body.

Hence, the correct sequence is:

Oogonia, Graafian follicle, Primary oocytes, Secondary oocytes, Ova.