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Tips for Cell division
Mitosis
Identification of Mitosis stages:
Prophase:
 Disappearing of nucleus
 Condensation of chromoatid reticulum
 Distinction of chromosomes
 Aster formation
 Appearance of spindle fibre
 Disappearance of nuclear membrane and nucleolus
 Attachment of sister chromatids at centromere
 Movement of centriole to the opposite poles
Metaphase:
 Attachment of spindle with the centromere
 Lining of chromosome in plane at equator.
Anaphase:
 Contraction of spindle fibre
 Division of centromere
 Separation of two sister chromatids of each chromosome
 Movement of separated sister chromatids towards the opposite pole
 Furrow formation ( animal cell)/ cell plate formation ( plant cell)
Telophase:
 Formation of two sets of chromosomes in opposite pole
 Reappearance of chromosomes
 Reappearance of nuclear membrane
 Deepening of furrow formation
 Reappearance of nucleolus
 Division of cytoplasm
 Formation of two daughter cells
Cell cycle:
The sequence of events that occurs between the cell formation and its division. It includes Interphase and
mitosis.
G1 phase:
 Division of mitochondria and chloroplast
 Synthesis of RNA and protein
S Phase/ Synthesis phase:
 Synthesis of DNA
 Duplication of chromosomes
G2phase:
 Synthesis of protein
Meiosis:
Leptotene:
 Condensation and shortening of chromatin network
 Formation of centriole and moving towards to opposite poles
Zygotene:
 Pairing of homologous chromosomes (synapsis)
 Formation of bivalent
Pachytene:
 Formation of chiasmata
 Formation of tetrad
 Exchange of chromosome segments ( Crossing over)
Diplotene:
 Movement of paired homologous chromosomes away from each other
Diakinesis:
 Shortening and condensation of homologous chromosomes
 Disappearance of nucleolus and nuclear membrane
 Movement of centrioles
Crossing over:
It is an exchange of portions of chromatids between two nonsister chromatids of
homologous chromosomes. It takes place in pachetene of prophase I of Meiosis I.
Chromosomes:
Autosomes:
These are body chromosomes which express body character of the organism. In human beings
22pairs of autosomes are seen.
Allosomes:
These are sex chromosomes which express sex of the individual. In human beings 1 pair of
allosome is seen.
Haploid:
A cell with single set of chromosomes is called haploid cell. It is represented as ‘n’.
Eg; Sperm and Egg
Diploid:
A cell with two sets of chromosomes is called diploid cell. It is represented as ‘2n’.
Eg; Body cells
Nucleosome:
The histone and DNA form a kind of complex in which the DNA strand winds around a core of eight
histone molecules. Each such molecule is called nucleosomes.
DNA:
Nucleotide:
It is a part of DNA which consists of deoxy ribose sugar, Phosphate and nitrogenous base.
Nucleoside:
It is a part of DNA which consists of deoxy ribose sugar and Nitrogenous base.
Gene:
It is a part of DNA which expresses a particular character of the organism.
Homologous chromosomes:
A pair of corresponding chromosomes of the same shape and size, one from each
parent.
Replication of DNA:
Synthesis of DNA is called Replication of DNA. It takes place during s-phase of interphase.
Check your progress:
Level: 1
I. Name the following:
1 )Division which brings about vegetative growth
2) The phase usually skipped in meiosis
3) Crossing over occurs during this substage of meiosis
4) Phase when the cell plate begins in the centre and moves towards the cell wall.
5) The stage when sister chromosomes separate from their paired condition
6) The stage in mitosis when the nucleolus starts overlapping
7) The shortest phase of mitosis
8) The phase in mitosis when the nucleolus starts disappearing
9) The structure that attaches to the spindle during metaphase of mitosis.
10) The structure from which the spindle forms in an animal cell.
11) The phase when two chromatids divides and the two sister chromatids of each chromosome
Separate and are drawn apart toward opposite poles.
12) The largest phase of a normal cell. Cycle.
13) The process during which the meiosis occurs in human beings
14) The stage of meiosis at which there are two cells, each with sister chromatids aligned at the
Equator.
15) The shortest phase of cell cycle
16) The type of cell division that occurs during growth of shoot.
17) The repeating components of each DNA strand length wise.
18) The stage in which nuclear membrane reappear.
19) The kind of cell division that takes place in meristem
20) The kind of cell division that takes place in gonads.
II. Fill in the blanks:
1) Karyokinesis means division of ____________.
2) The spindle fibres are made up of ______________.
3) The type of cell division that takes place in Androecium and gynoecium is ______.
4) The chromatids are attached to each other at ____________.
5) The process by which gametes are formed is called _________.
6) The growth of the organism is achieved by ___________ division.
7) The first stage of cell division is _______________.
8) Chromosomes arrange at equatorial plate of division spindle at ___________.
9) The number of chromosome is ____________ in meiosis.
10) Replication of DNA occurs in the _____________ of the interphase
11) The region of the attachment of chromosomes to spindle fibres is called ________.
12) A cell has 8 chromosomes. After meiotic cell division, the number of chromosomes in the
Daughter cells will be __________.
13) Crossing over takes place during ____________ stage of meiosis.
III.Define the following:
1) karyokinesis 2) cytokinesis 3) Asters 4) Homologous chromosomes 5) synapsis
6) bivalent 7) Crossing over 8) chiamata 9) Haploid cell 10) Diploid cell 11) Chromosome
12) Chromatid 13) Autosomes 14) Allosomes 15) Karyotype 16) Centromere 17) cell cycle
18) Chromatin reticulum 19) nucleosome 20) Nucleotides 21) Nucleotides 22) Interphase
IV. Name the stages of meiotic cell division showing following events:
1) Condensation and shortening of chromatin network
2) The paired homologous chromosomes begin to move away from each other.
3) The homologous chromosomes attract each other and lie in pairs
4) The nonsister chromatids of a tetrad twist each other and exchange of some genes portion
takes place between the two.
5) Nuclear membrane reappears around the chromatin network leading to formation of two
daughter nuclei.
V.Matching:match the term to the description
A. Prophase
B. Interphase
C. Telophase
D. Metaphase
E. Anaphase
__ 1. The sister chromatids are moving apart.
__ 2. The nucleolus begins to fade from view.
__ 3. A new nuclear membrane is forming
around the chromosomes.
__ 4. The cytoplasm of the cell is being divided.
__ 5. The chromosomes become invisible.
__ 6. The chromosomes are located at the
equator of the cell.
__ 7. The nuclear membrane begins to fade from
view.
__ 8. The division (cleavage) furrow appears.
__ 9. The chromosomes are moving towards the
poles of the cell.
__ 10. Chromatids line up along the equator.
__ 11. The spindle is formed.
__ 12. Chromosomes are not visible.
__ 13. Cytokinesis is completed (as next cycle
begins).
__ 14. The cell plate is completed.
__ 15. Chromosomes are replicated.
__ 16. The reverse of prophase.
__ 17. The organization phase
.
VI Fill in the blank: Some will be used more than once.
A. Prophase
B. Interphase
C. Telophase
D. Metaphase
E. Anaphase
F. Centromere
G. Chromatid
H. Cytokinesis
I. Mitosis
J. Spindle fiber
K. Cell plate
________18. What phase are daughter cells in as a result of mitosis?
________19. During what phase of mitosis do centromeres divide and the chromosomes move
toward their respective poles?
________20. What is the phase where chromatin condenses to form chromosomes?
________21. What is the name of the structure that connects the two chromatids?
________22. In a chromosome pair connected by a centromere, what is each individual
chromosome called?
______23. What are the two parts of cell division?
_______24. What structure forms in prophase along which the chromosomes move?
_______25. Which phase of mitosis is the last phase that chromatids are together?
________26. Which phase of the cell cycle is characterized by a non-dividing cell?
_______27. What structure is produced when protein fibers radiate from centrioles?
________28. What forms across the center of a cell near the end of telophase?
____29. The period of cell growth and development between mitotic divisions?
____30. What is the phase where cytokinesis occurs?
Level : 2
I) Given below is a diagram representing
a stage during mitotic cell division in a
cell.
i) Identify the above stage. Give two reasons to support your answer.
ii) Label the parts 1 to 4.
iii) Name the structure that forms the part 3.
iv) Name the stage that follows this stage of mitosis. How can this stage be identified?
v) Mention two points of difference between mitosis and meiosis with regard to:
1) The number of daughter cells formed
2) The ploidy nature of the daughter cells.
II 1) Draw a labeled diagram to show the metaphase stage of mitosis in an
animal cell having chromosomes.
2) How many daughter cells are formed at the end of mitosis and at the
end of meiosis?
3) With reference to cell division explain the following terms:
Chromatid, Centromeres, Haploid
4) Name the type of cell division that occurs during:
i) growth of shoot
ii) formation of pollen grains
iii)repair of worn out tissues
III)Given below is a diagram of a double helical structure of DNA:
i)Name the four nitrogenous bases that form a DNA molecule.
ii) Give the full form of DNA
iii)What are nuclesides and nucleotides?
IV) Given below is a schematic diagram of a portion of a DNA.
i) How many strands is it showing?
ii) How many nucleotides have been shown in each strand?
iii) Label the parts numbered 1, 2,3,4 and 5.
v) Differentiate between the following based on the instruction given in the brackets:
i) Mitosis and Meiosis ( No. of cells formed and place of occurrence)
ii) Chromosome and chromatin reticulum ( definition)
iii) Haploid and Diploid ( Definition and Example)
iv) Centrosome and centromere ( function)
v) Nucleotide and Nucleoside ( definition)
vi) Cytokinesis and Karyokinesis
vii) Cytokinesis in plant cell and animal cell( pattern)
viii) DNA and RNA ( expansion and Nitrogenous base)
ix) Mitosis in Plant cell and Animal cell ( aster and centriole)
vi)
Level : 3
I. Brain corner:
A bacteria cell divides once every minute, It takes an hour to fill up a cup.
How much time will it take to fill half a cup?
II. Write a note on PCD (programmed cell death)
III. How do we get cancer?