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प्रश्न
With the help of suitable diagrams, explain the five stages of prophase-I of meiosis.
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उत्तर
Prophase-I is the first stage of meiosis-I and is the longest and most important stage. It is divided into five sub-stages:
1. Leptotene
- Chromosomes begin to condense.
- They become long, thin, and distinct.
2. Zygotene
- Homologous chromosomes pair together by a process called synapsis.
- A synaptonemal complex is formed.
- Paired chromosomes form bivalents or tetrads.
3. Pachytene
- It is the longest stage of Prophase-I.
- Chromosomes become shorter and thicker.
- Crossing over occurs between non-sister chromatids of homologous chromosomes.
- Recombination nodules appear at crossing-over sites
4. Diplotene
- Synaptonemal complex dissolves.
- Homologous chromosomes begin to separate.
- Chiasmata appear at crossover points.
5. Diakinesis
- Chiasmata terminalise.
- Chromosomes condense further.
- The nuclear membrane and nucleolus disappear.
- Meiotic spindle fibres begin to form.
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संबंधित प्रश्न
The diagram given below represents a stage during cell division.
Study the same and answer the questions that follow:
- Identify whether it is a plant cell or an animal cell. Give a reason in support of your answer.
- Name the stage depicted in the diagram. What is the unique feature observed in this stage?
- Name the type of cell division that occurs during:
- Replacement of old leaves by new ones
- Formation of gametes
- What is the stage that comes before the stage shown in the diagram?
- Draw a neat, labelled diagram of the stage mentioned in (iv) above keeping the chromosome number constant.
Given below is a diagram representing a stage during mitotic cell division in an animal cell Examine it carefully and answer the questions which follow.
- Identify the stage. Give one reason in support of your answer.
- Name the cell organelle that forms the ‘aster’.
- Name the parts labelled 1, 2 and 3.
- Name the stage that follows the one shown above; how is that stage identified?
- Mention two differences between mitosis and meiosis with regards to:
- The number of daughter cells produced.
- The chromosome number in the daughter cells.
Define the following:
Karyokinesis
Choose the correct answer:
Which division takes most time?
Choose the correct answer:
Nuclear membrane reappears in ____________
In which one of the following options the two stages of mitosis have been given in correct sequence?
Explain the Term Pachytene
Explain the Term Cell Diakinesis
Complete the following sentence with appropriate word :
Colchicine arrests cell division at __________.
Mention, if the following statement is True or False. If false rewrite the wrong statement in its correct form:
The alkaloid colchicine inhibits the formation of the mitotic spindle.
Multiple Choice Question:
The nuclear membrane disappears in
Multiple Choice Question:
The nuclear membrane and nucleolus become indistinguishable during
Write the functional activity of the following structure:
Colchicine
