IMAT 2017 Q25 [Oogenesis]

The pathway shows some of the cells produced during oogenesis in the ovary of a healthy human female.

Which of the following cells in the pathway are diploid?

  1. germinal epithelial cells in the ovary
  2. oogonia
  3. primary oocyte
  4. secondary oocyte

A. 1, 2 and 3 only
B. 1 only
C. 4 only
D. 1, 2, 3 and 4
E. 2, 3 and 4 only

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The correct answer is A.

But first, what is a diploid cell ?

A diploid cell has 2 complete sets of chromosomes, usually written as being a 2n cell, as opposed to a haploid cell, that only has 1 set of each chromosome, and written as a n cell.

All the body cells are diploid, except for the gametes. From that only, we can determine that item 1, the germinal epithelial cells in the ovary, is correct.

Now, what is oogenesis ?

It is the process that ultimately leads to the production of ovules in ovaries.

  • The process begins with a diploid cell, the oogonia (2n), which goes through mitotic divisions and forms the primary ovocyte (2n). This signs the end of the first meiosis and the beginning of the second one.
  • Then we have the formation of the secondary ovocyte (n) and the first polar body (n).
  • After ovulation and fecondation, the second meiosis is completed and we have the formation of the second polar body (n) and the fertilized egg (n).

Knowing that, we can determine that the items 2 and 3 are correct and that 4 is incorrect, making answer A the right one.