study the given flow chart carefully and answer the questions given below.
Oogonia------ Mitosis----- Primary Oocyte------ Meiosis I --------- Secondary Oocyte + Polar body --------Meiosis II------------- Ovum + II Polar body.
Why is Meiosis I an equational division?
When and where does Meiosis II occur?
All the events of menstrual cycle stpo during pregnancy.Why?

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Solution

1.Meiosis I is known as the equational division as it reduces the number of sets of chromosomes to half of its original number(46 chromosomes are converted to 23 chromosomes).
2. Meiosis II occurs after meiosis I when the chromosomes sets are reduced to half of its original number. It is similar to mitosis. It results in the formation of four haploid cells from two haploid cells inside the nucleus of the cells.
3.During pregnancy as the ovum is released during menstrual cycle, it is fertilised by the incoming sperm and this leads to increase in progesterone level to set the pregnancy.. The zygote is implanted in the uterus and this prevents the thickening of the uterine lining which cause mentrual discharge.

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Similar questions

Q. Following statements are given w.r.t. gametogenesis.
(a) Meiosis

1^{s t}

occurs in primary oocyte
(b) Meiosis

2^{n d}

may start but can’t be completed in virgin woman’s secondary oocyte
(c) Meiosis

1^{s t}

is completed in follicular phase of menstrual cycle
(d) Meiosis

2^{n d}

produces three polar bodies and one ovum
From above

Oogonia go through____(i)____ during the first three months of fetal development, producing all the primary oocytes. Primary oocytes begin the process of meiosis but are halted in___(ii)____. Meiosis resumes, one oocyte at a time, beginning with the first ___(iii)______. This process is stimulated by ____(iv)_______. The secondary oocyte is arrested in ____(v)_____.

Q. How many structures in the list given below are diploid?
Spermatid, secondary oocyte, primary spermatocyte, ovum, sperm, oogonia, spermatogonia, polar body

Q. At fertilization, meiosis-II completes in the ovum, forming a second polar body.

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