Question

Describe multiplication phase, growth phase and maturation phase

Answer 1

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I. Multiplication phase:

In this stage, the

primary germinal cells PGCs (2n) of ovary

undergo repeated mitotic division to form

millions of gamete mother cells or oogonial

cells (2n). This process is completed in the

embryonic stage of human females.

II. Growth phase:

Some of the oogonia stop

division and begin to increase in size and form

the primary oocytes (2n). Cellular organelles

like ER, golgi appratus and mitochondria

increase in number.

III. Maturation phase:

Oogenesis takes place

in the ovaries. The process is initiated prior to

birth of the female baby. The primary oocytes

(2n) enter the maturation phase which includes

meiotic division (Meiosis I and Meiosis II).

The diploid primary oocytes undergo meiosis I

(reduction division) to form 2 haploid daughter

cells. This division is peculiar in females

as both the daughter cells are with haploid

number of chromosomes i.e. 23 chromosomes.

But due to unequal division of cytoplasm, of

the 2 daughter cells produced, one is a large

cell called secondary oocyte (n) and another is

a small cell called 1st polar body (n). Normally

the 1st polar body does not enter meiosis II.

The secondary oocyte (n) proceeds meiosis II,

only upto metaphase II. It’s division is further

stopped or arrested at this stage. The secondary

oocyte is shed from the graafian follicle and

ovary. The restart and completion of meiosis II

will happen only with entry of the sperm. This

last phasand is ready for fertilization. (Completion of

meiosis II and completion of fertilization go

hand in hand. If the secondary oocyte does not

receive the sperm / spermatozoa, it is shed off

along with menstrum).

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Answer 2

Answer:

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