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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 longest phase of meiosis and is further sub divided into 5 phases:
- Leptotene
Condensation makes chromosomes become distinct and compact. - Zygotene
Homologous chromosomes start pairing together by a process called synapsis to form a complex structure called synaptonemal complex. Two synapsed homologous chromosomes form a complex called bivalent or tetrad. - Pachytene
Longest phase of prophase I
Recombination nodules appear in this stage at the sites where crossing over has to take place between non-sister chromatids of homologous chromosomes. - Diplotene
Synaptonemal complex dissolves and recombinants separate from each other except at crossover sites to form X-shaped structure called chiasmata. - Diakinesis
Chiasmata terminalises and chromosomes condense. Meiotic spindle assembles and nucleolus and nuclear envelope disappear.
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संबंधित प्रश्न
The diagram given below represents a certain stage of mitosis:
- Identify the stage of cell division.
- Name the parts labelled A and B.
- What is the unique feature observed in this stage?
- How many daughter cells are formed from this type of cell division?
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.
Fill in the blank:
______ takes place in body cells resulting in growth and development.
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.
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
Name the stage during which nuclear membrane and nucleoli reappear.
Name the Following
Nuclear envelope and nucleoli reappear in which stage.
Give Technical Terms
The stage in mitosis when the nucleolus starts disappearing.
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
During Mitosis what is the position of chromatids in the anaphase?
