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Question
With the help of suitable diagrams, explain the five stages of prophase-I of meiosis.
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Solution
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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RELATED QUESTIONS
Fill in the blank and explain the statement.
All chromosomes are arranged parallel to equatorial plane of cell in ______ phase of mitosis.
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.
Choose the correct answer:
Which division takes most time?
Choose the correct answer:
Nuclear membrane reappears in ____________
Differentiate between Centrosome and centromere.
Identify the stages of mitosis given below and label the figures.
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Name the following:
The kind of division normally seen at the tip of the root and shoot system.
Give Technical Terms
The stage in mitosis when the nucleolus starts disappearing.
Give Technical Terms
Division of nucleus.
Complete the following sentence with appropriate word :
______means the splitting of the nucleus.
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The alkaloid colchicine inhibits the formation of the mitotic spindle.
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. |
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?
In which stage of mitosis the chromosomes align in an equatorial plate? How?
Identify the stage of mitosis from the below picture. List the chromosomal events in this stage.
