Slide 1 : APT ACADEMIC SOLUTIONS
Slide 2 :
Slide 3 :
Slide 4 : Session Objectives Cell cycle
To Study the types of cell division
Mitosis
Meiosis
Amitosis
Endomitosis
c-Mitosis
Significances of different types of cell reproduction
Cell Cycle : Cell Cycle Interphase
Cell Cycle : Cell Cycle Phases of Cell
Cycle are
G1
S
G2
M
Phases of Cell Cycle : Phases of Cell Cycle G1 Phase Proteins are synthesized
Proteins are enzymatic in nature S Phase DNA are synthesized
Histone proteins are synthesized
Slide 8 : Phases of Cell Cycle G2 Phase Proteins are synthesized
Proteins are structural in nature
Tubulin proteins are synthesized
Genetic material can be represented as 4C M Phase Divided into Karyokinesis & Cytokinesis What is G0 phase ?
Mitosis : Mitosis Mitosis Cytokinesis
Interphase : Interphase Metabolically
the most active
Stage
Indistinct
chromosome
Intact nuclear
membrane
Centriole divides
Prophase (Early) : Prophase (Early) Condensation of
Chromosome
Chromosome splits into Chromatids
Nuclear membrane &
nucleolus remain intact
Prophase (Late) : Prophase (Late) Chromatids are randomly
distributed in cell
Nuclear membrane &
nucleolus disappear
Spindle fibres are formed &
attached to centromere
Metaphase : Metaphase Chromosome are fully
condensed
Chromatids are arranged
at the equatorial plate
called metaphase plate
Best stage for the study
of chromosome
Anaphase : Anaphase Centromere divides
Spindle fiber contracts
Chromatids become
V-shape
Chromatid moves to
their respective poles
Telophase : Telophase Reverse to Prophase
Condensation of
chromosome occurs
Chromosome become
thicker & thinner
Spindle fibre disorganize
Nuclear membrane &
nucleolus reapperars
Cytokinesis : Cytokinesis Plants ER, Golgi bodies & IZ fibre form Fragmoplast
Fragmoplast forms cell plate
Cell plate formation is centripetal
Cytokinesis : Cytokinesis Animal ER, Golgi bodies & IZ fibre form midbody
Midbody helps in the formation of cell furrow
Centrifugal pattern
Illustrative Problem : Illustrative Problem Mitosis can be best studied in ? Root tips
Shoot tips
Leaf tips
Floral tis Root tips lacks natural pigments, hence,
chromosome can be easily stained
Illustrative Problem : Illustrative Problem What is the number of mitotic division required to form 100 cells ? 25
50
99
100 No. of Mitotic Div. = n – 1
Where n = no. of cells
Meiosis : Meiosis Meiosis was first noticed by Strasburger in 1888, although the term meiosis was coined in 1905 by J.B. Farmer and J.E. Morre
Occurs in germ cells
Immature anther is the best material to study the division
Four daughter cells are formed
Chromosome number is reduced by half
Meiosis : Meiosis Interphase Cytokinesis
Meiosis I : Meiosis I Chormosome appear
As thin thread like
structure Bouquet Arrangement
are observed Nuclear membrane &
nucleolus remains
intact
Meiosis I : Meiosis I Condensation of chromosome
occurs Homologous chromosomes
get paired The pairing is known as
synapsis or syndesis Pairing occurs with the
help of synaptonemal
complex
Meiosis I : Meiosis I Condesation results into
spliting of chromosome
into chromatids & tetrads
are formed Exchange of genetic
materials takes place
between non-sister
chromatids & the process
is known as crossing over The regions where crossing
over takes place are called
chiasmata
(singular chiasma)
Meiosis I : Meiosis I Homologous chromosomes
repel each other Terminalization of the
chiasma begins Synaptonemal complex
disorganizes
Meiosis I : Meiosis I Nuclear membrane &
nucleolus disappear Spindle fibres are
formed Chiasma fully
terminalized
Meiosis I : Meiosis I Metaphase I Chromosome organize
themselves at the
equatorial plate
Meiosis I : Meiosis I Anaphase I Disjunction of the
chromosome Contraction of the
spindle fibre resulting
into movement of the
chromosome at their
respective poles Actual reduction in the
chromosome no.
Meiosis I : Meiosis I Telophase I
Meiosis : Meiosis Intrameiotic Interphase (Interkinesis) Stage between telophase of first meiotic division and prophase of second meiotic division No replication of DNA Similar to Interphase except the S- Phase
Meiosis II : Meiosis II Prophase II
Meiosis II : Meiosis II Metaphase II
Meiosis II : Meiosis II Anaphase II
Meiosis II : Meiosis II Telophase II and Cytokinesis
Slide 35 : Centromere on the
metaphase plate Arms are directed
towards the pole Centromere directed
towards the pole Arms are on metaphase plate
Slide 36 : Centromere divides Disjunction of the chromosome Metaphase Anaphase
Significance of meiosis : Significance of meiosis Crossing over in meiosis enables genetic
variation in organisms
Compensates for the doubling of chromosomes
at gametic fusion and thus helps to keep the
number of chromosomes constant
Variations coupled with heredity leads to
organic evolution
Illustrative Problem : Illustrative Problem What is the number of meiotic division required to form 100 male gamete ? 25
50
99
100 No. of meiotic div. = n / 4
Where n = no. of male gamete
Illustrative Problem : Illustrative Problem What is the number of meiotic division required to form 102 male gamete ? 25
26
27
25.5 Gametes can be formed only after
completion of the division
Illustrative Problem : Illustrative Problem What is the number of meiotic division required to form 100 female gamete or egg cell ? 25
50
99
100 During the formation of the female
gamete, 3 cells degenerate and
only one survive to develop into
egg cell
Hence, No. of meiotic div. for
egg cell = n,
where n = no. of egg cell
Illustrative Problem : Illustrative Problem What is the number of meiotic division required to form 100 seeds ? 25
50
100
125
Illustrative Problem : Illustrative Problem What is the number of meiotic division required to form 103 seeds ? 128
128.5
128.75
129
Slide 43 :