Answer
384.6k+ views
Hint: Meiosis takes place in special cells at specific times. Meiosis occurs in cells called meiocytes which are oocytes, spermatocytes and sporacytes. Two successive divisions produce four daughter cells. The term meiosis was introduced by J.B. Farmer and Moore in 1905.
Complete answer:
By Meiosis a parent cell produces four daughter cells, having half the number of chromosomes and half of the nuclear DNA to that of the parent cell. Thus, it is also known as reduction division. Two divisions of Meiosis- Meiosis-I and Meiosis-II.
Meiosis-I is known as heterotypic division. In this division, the two homologous chromosomes of each pair separate from each other and go to separate daughter cells. Thus, the number of chromosomes from diploid to haploid condition. There are four phases of Meiosis-I which are-prophase-I, metaphase-I, anaphase-I and telophase-I.
Brief description of Prophase-1:
It lasts for a long time. It has five sub – phases:
i. Leptotene
ii. Zygotene
iii. Pachytene
iv. Diplotene
v. Diakinesis
i. Leptotene-Characteristics of leptotene are:
Beaded, long chromosomes.
Chromosomes show bouquet arrangement.
ii. Zygotene –
Chromosomes become shorter and thicker.
Bivalents or tetrads (paired homologous chromosomes) are seen.
Synapsis occurs
Bivalents form synaptonemal complexes.
iii. Pachytene –
It is the longest stage, where tetrads clearly appear as spirally arranged chromosomes of homologous pairs.
Crossing over occurs in this stage.
iv. Diplotene –
In this stage bivalents repel each other.
Chiasmata appears.
In oocytes of vertebrates it lasts for months or years.
v. Diakinesis –
Nuclear membrane disappears, centrioles migrate to poles and spindle fibres begin to form.
Note: In diplotene, the chromosomes may unfold and start transcription of mRNA and rRNA build up food reserve in the cytoplasm. Example: In primary oocytes of amphibians, reptiles and birds. In some species chromosomes enlarge greatly, like lampbrush form.
Complete answer:
By Meiosis a parent cell produces four daughter cells, having half the number of chromosomes and half of the nuclear DNA to that of the parent cell. Thus, it is also known as reduction division. Two divisions of Meiosis- Meiosis-I and Meiosis-II.
Meiosis-I is known as heterotypic division. In this division, the two homologous chromosomes of each pair separate from each other and go to separate daughter cells. Thus, the number of chromosomes from diploid to haploid condition. There are four phases of Meiosis-I which are-prophase-I, metaphase-I, anaphase-I and telophase-I.
Brief description of Prophase-1:
It lasts for a long time. It has five sub – phases:
i. Leptotene
ii. Zygotene
iii. Pachytene
iv. Diplotene
v. Diakinesis
i. Leptotene-Characteristics of leptotene are:
![seo images](https://www.vedantu.com/question-sets/5607003c-af8e-4160-9c57-85d6950b8e086167881037455042.png)
Beaded, long chromosomes.
Chromosomes show bouquet arrangement.
ii. Zygotene –
![seo images](https://www.vedantu.com/question-sets/08ea256e-7b96-4adc-a74e-543845a4662f6976403608407232439.png)
Chromosomes become shorter and thicker.
Bivalents or tetrads (paired homologous chromosomes) are seen.
Synapsis occurs
Bivalents form synaptonemal complexes.
iii. Pachytene –
![seo images](https://www.vedantu.com/question-sets/74b56b9c-7c08-4331-b907-7ee70d5accbc714268888486190519.png)
It is the longest stage, where tetrads clearly appear as spirally arranged chromosomes of homologous pairs.
Crossing over occurs in this stage.
iv. Diplotene –
![seo images](https://www.vedantu.com/question-sets/2d8f07ef-5c2e-42b6-af5e-4b74d039ab9d1833276063055092292.png)
In this stage bivalents repel each other.
Chiasmata appears.
In oocytes of vertebrates it lasts for months or years.
v. Diakinesis –
![seo images](https://www.vedantu.com/question-sets/b62a3cd6-2a1b-40d0-b0da-d3d53eaf150f7961262168779380258.png)
Nuclear membrane disappears, centrioles migrate to poles and spindle fibres begin to form.
Note: In diplotene, the chromosomes may unfold and start transcription of mRNA and rRNA build up food reserve in the cytoplasm. Example: In primary oocytes of amphibians, reptiles and birds. In some species chromosomes enlarge greatly, like lampbrush form.
Recently Updated Pages
How many sigma and pi bonds are present in HCequiv class 11 chemistry CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Why Are Noble Gases NonReactive class 11 chemistry CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let X and Y be the sets of all positive divisors of class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let x and y be 2 real numbers which satisfy the equations class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let x 4log 2sqrt 9k 1 + 7 and y dfrac132log 2sqrt5 class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let x22ax+b20 and x22bx+a20 be two equations Then the class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Trending doubts
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Which are the Top 10 Largest Countries of the World?
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Write a letter to the principal requesting him to grant class 10 english CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Give 10 examples for herbs , shrubs , climbers , creepers
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Fill in the blanks A 1 lakh ten thousand B 1 million class 9 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Change the following sentences into negative and interrogative class 10 english CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Difference Between Plant Cell and Animal Cell
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Differentiate between homogeneous and heterogeneous class 12 chemistry CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)