Question

युग्मक जनन को परिभाषित कीजिए Oogenesis की प्रक्रिया का वर्णन कीजिए

Answer 1

Answer:

युग्मक युकैरियोटिक प्रकार की जनन कोशिका हैं। इनका निर्माण युग्मक जनन की क्रिया में माइटोसिस कोशिका विभाजन के फलस्वरुप होता है। पुरुषों की जनन कोशिका को शुक्राणु तथा स्त्रियों की जनन कोशिका को अंडाणु कहते हैं।

प्रजनन की वह क्रिया जिसमें दो युग्मकों के मिलने से बनी रचना युग्मज (जाइगोट) द्वारा नये जीव की उत्पत्ति होती है, लैंगिक जनन (sexual reproduction) कहलाती है।[1] यदि युग्मक समान आकृति वाले होते हैं तो उसे समयुग्मक कहते हैं। समयुग्मकों के संयोग को संयुग्मन कहते हैं। युग्मनज या तो सीधे पौधे को जन्म देता है या विरामी युग्मनज बन जाता है जिसे जाइगोस्पोर कहते हैं। इस प्रकार के लैंगिक जनन को 'समयुग्मी' कहते हैं।

लैंगिक जनन की प्रक्रिया के दो मुख्य चरण हैं - अर्धसूत्री विभाजन तथा निषेचन (fertilization)।

लैंगिक जनन की उत्पत्ति कैसे हुई, यह एक पहेली है। इस विषय में कई व्याख्याएँ प्रस्तुत की गईं हैं कि अलैंगिक जनन से लैंगिक जनन क्यों विकसित हुआ।

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Answer 2

Gametogenesis (Spermatogenesis and Oogenesis) is a biological process in which maturation of gametes takes place.

Explanation:

Gametogenesis occurs through the process of meiotic division of diploid gametocytes into separate gametes or by mitosis. In gametophytes, for instance, plants produce gametes by mitosis.

Animals develop gametes in organs called gonads (testis in males and ovaries in females) directly by meiosis from diploid mother cells. Males and females of a sexually reproductive species have various types of gametogenesis that involves spermatogenesis (male) and oogenesis (female).

Oogenesis is defined as the transformation of the ovum or egg cell into a cell that is capable of further growth when fertilized. This is formed through maturation from the primary oocyte and initiated in the embryonic stage.

The oogenesis cycle starts before birth from the creation of oogonia, a diploid germ cells, which further grow into mature ovas.

Stages before birth:

1. oogonium duplicates their genetic material and further primary get arrested in prophase 1 until the first ovulation.

Stages during puberty (during childhood ovray remain inactive:

1. Primary oocyte undergoes meiosis phase and produces two daughter cells each with equal number of chromosomes.
2. As only one daughter cell is able to receive cytoplasm from primary oocyte that further produces secondary oocyte, the other daughter cell will get degenerate and called as first polar body.
3. During ovulation, ovary releases secondary oocyte thta carries two copies of chromosome. A mature ovum would have one collection and not two chromosomes. And the oocyte undergoes a second meiotic division.
4. The secondary oocyte get arrested in metaphase 2 before fertilization. When the sperm comes in contact with secondary oocyte it causes the second meiotic division which further give rise to mature egg. Due to unequal division of chromosomes, second polar body is made. The mature ovum remain attached with single set f chromosomes.
5. The process is completed only if secondary oocyte get fertilized by a sperm within a day and if it did not get fertilized the secondary oocyte will get degenerates.

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