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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.
APPEARS IN
संबंधित प्रश्न
Describe anaphase in mitosis.
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.
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?
Draw a labeled schematic representation of mitosis cell division.
Name the following:
The kind of division normally seen at the tip of the root and shoot system.
Name the Following
The stage when chromosomes arrange at the equator.
Name the Following
Name the stage during which nuclear membrane and nucleoli reappear.
Give Technical Terms
Division of nucleus.
Choose the Odd One Out
The karyotype (set of chromosomes) shown below is taken from a dividing cell in a certain individual.
(i) Is the individual male or female? Explain your answer.
(ii) How would you expect
(a) a female cell and
(b) sperm cell to differ in chromosome composition?
Explain the following figure.
Give the sequence of the events occurring during the prophase of mitosis.
The diagram given below represents a stage in mitosis.
- Identify the stage given above.
- Give one reason to support your answer in (a).
- Mention the number of chromosomes given in the diagram.
