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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 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.
The diagram below represents a stage during cell division. Study the same and then answer the questions that follow:
- Name the parts labelled 1, 2, and 3.
- Identify the above stage and give a reason to support your answer.
- Mention where in the body this type of cell division occurs.
- Name the stage prior to this stage and draw a diagram to represent the same.
Genetic recombination occurs in ______ phase of prophase of meiosis-I.
Describe anaphase in mitosis.
Fill in the blank:
______ is the indirect cell division.
In which one of the following options the two stages of mitosis have been given in correct sequence?
Differentiate between Centrosome and centromere.
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.
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
The stage in mitosis when the nucleolus starts disappearing.
Give Technical Terms
The stage at which spindle fibres begin to be formed.
Complete the following sentence with appropriate word :
______means the splitting of the nucleus.
Multiple Choice Question:
The nuclear membrane disappears in
