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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.
All chromosomes are arranged parallel to equatorial plane of cell in ______ phase of mitosis.
Define the following:
Karyokinesis
Fill in the blank:
______ is the indirect cell division.
The diagram given alongside represents a stage in cell division.
Study the same and answer the questions that follow:
(i) Identify the stage of cell division.
(ii) Name the parts labeled A,B,C and D.
(iii) What is the unique feature observed in this stage?
(iv) Where does this type of cell division usually occur?
(v) How many daughter cells are formed from this type of cell division?
(vi) Is the dividing cell shown a plant or an animal cell?
Give a reason to support your answer.
The fig given alongside shows a certain stage in a cell division in a cell with four chromosomes.
(i) Name the parts of the chromosome labeled A and B.
(ii) Name the structure C. what is its function?
(iii) Name the type of division . Give a reason.
(iv) Name the stage of division.
(v) Name the stages before and after the stage shown in diagram.
In which one of the following options the two stages of mitosis have been given in correct sequence?
Differentiate between Centrosome and centromere.
The figure below shows a certain stage of mitosis:
(i) Name the stage,
(ii) Label the parts 1 to 4
(iii) How many chromosomes are shown here?
Name the following:
Mitosis takes place in which cells.
Name the following:
The kind of division normally seen at the tip of the root and shoot system.
Complete the following sentence with appropriate word :
Colchicine arrests cell division at __________.
Choose the Odd One Out
Multiple Choice Question:
The nuclear membrane and nucleolus become indistinguishable during
Column ‘II’ is a list of items related to ideas in Column ‘I’. Match the terms in Column ‘II’ with a suitable idea given in Column ‘I’.
| Column I | Column II |
| (i) Anaphase | (a) Chromosomes become arranged in a horizontal plane at the equator. |
| (ii) Prophase | (b) Daughter chromosomes move to opposite poles of the spindle. |
| (iii) Telophase | (c) Chromosomes become visible as fine, long threads. |
| (iv) Metaphase | (d) Chromosomes lose their distinctiveness and gradually become transformed into chromatin network. |
During Mitosis what is the position of chromatids in metaphase?
The phase of karyokinesis which is almost the reverse of prophase is ______.
