Cell Division Flashcards
Cell Cycle?`
The sequence of events by which a cell duplicates its genome, synthesizes other constituents of the cell and eventually divides into two daughter cells.
The period between the formation of new daughter cells and their further divisions.
Cell Cycle
2 phases of cell cycle?
1) Interphase
2) M / Mitotic Phase
Phase between two successive M phase
Interphase
The Cell prepares itself for cell division in
Interphase
Biosynthetic phase in which cell duplicates its organelles and replicates its DNA (95% of the cell cycle)
Interphase
Actual cell divison occurs in
M phase
in what phase does the cell utilises the constituents formed during interphase and divide into 2 daughter cell
M phase
period of cell cycle in yeast
90 minutes
period of cell cycle in (typical) human cell
24 hours
Long, Non-Dividing, Growing phase of the cell cycle
interphase
the most active stage of the cell cycle
interphase
resting phase (as no activity related to actual cell divison) aka
interphase
3 main stages of the interphase
1) G1 phase ( Pre-DNA synthesis phase/ post mitotic phase)
- –> G 0 phase - Quiescent Phase
2) S phase (DNA synthesis phase)
3) G2 phase- (post DNA synthesis phase/ pre mitotic phase)
The interval bw mitosis and initiation of DNA replication.
G1 phase
Cell is metabolically active but does not synthesize or replicate DNA in what phase/?
G1 phase
in G1 phase, the cell synthesizes?
nucleotides, ATP, proteins, amino acids, RNA etc
Most of the organelle duplication occurs in
G1 Phase
If a cell divides frequently then it has a SHORTER/ LONGER G1 phase?
Shorter G1 phase
if a cell does not divide frequently it has a ——— G1 phase?
Longer
The non-dividing cell enters the
G0 phase ( QUIESCENT Phase)
What happens in the G0 phase?
Cell remains metabolically active, but do not proliferate unless called to do so
Synthesis or DNA replication takes place in
S Phase
Cell doubles its DNA in (interphase)
S phase
The number of chromosomes after S phase…
Remain the same
Gap 2 phase is present bw
S and M Phase
Tubulin Protein synthesis takes place in what phase?
G2 Phase
Which organelles duplicate in the G2 phase?
Mitochondria, Chloroplast, Golgi Bodies
The DNA synthesis stops in the G2 phase? T or F
TRUE (but the cell synthesizes RNA, proteins etc.)
In animals, mitotic division is seen in
ONLY in diploid somatic cells
In plants, mitotic division is seen in
both haploid & diploid cells
the actual cell division occurs in
M Phase
The most dramatic period of cell cycle
M Phase
Distribution of the already duplicated components occurs in an orderly manner in — Phase/.
M Phase
M Phase consists of -
Karyokinesis & Cytokinesis
Karyokinesis?
where division of nucleus occurs during mitosis or meiosis
Cytokinesis?
where division of cytoplasm occurs during mitosis or meiosis
karyokinesis is divided into
prophase, metaphase, anaphase and telophase
Mitosis?
parent cell divides into two daughter cells, these cells are identical to each other as well as to parent cell
in mitosis both the daughter cells have ——- number of chromosomes
same number of chromosomes as present in parent cell
mitosis is called ——– division
equational
mitosis was first observed by
Strasburger in plant cell & Walter Flemming in animal cell.
the term mitosis was given by
Walter Flemming in 1882
mitosis also called
somatic cell division;
mitosis occurs in
somatic cells of animals
in the gonads for multiplication of undifferentiated germ cells
in plants: dividing meristematic tissue; and also in leaves, flowers and fruit during growth
first stage of Karyokinesis
Prophase
The chromosomes appear like a ball of wool called (____) in what phase?
Prophase, (Spireme Stage)
Cells do not show which organelles in prophase
Golgi complex, ER, Nuclear Membrane, Nucleolus
Events during Prophase
Condensation of Chromatin material
DNA untangles to form, compact mitotic chromosomes
Spireme stage
centrosome begin to move towards opposite poles of cell
second stage of mitosis
metaphase
what marks the beginning of metaphase?
the disintegration of the nuclear envelope
chromosomes in metaphase are
thickest and shortest
easiest to study chromosomal morphology in what phase
metaphase
what is congression?
the phenomenon of bringing the chromosomes to the equator of spindle
the surface of the centromere which holds the two sister chromatids of a chromosome is surrounded by a small disc shaped structure called
kinetochore
the spindle fibres are made up of
microtubules
site of attachment of microtubules
kinetochores present around centromere
the microtubules of spindle fibres attach to the kinetochore during
metaphase
in what phase do the chromatids move towards the poles
anaphase
events in anaphase
ref. pg 67
formation of interzonal fibres occurs in
anaphase
best stage to study shape of chromosomes (V,L,J,I)
Anaphase
end stage of karyokinesis
telophase
the chromosomes (sister chromatids) reach their respective poles in
telophase
disappearance and re-appearance of —– in telophase?
mitotic spindle disappears
nucleolus, endoplasmic reticulum, golgi bodies, REAPPEAR
phase that marks the end of cell division
cytokinesis
in some organisms , Karyokinesis is not followed by cytokinesis, this leads to formation of
Syncytium, i.e. a single cell containing large number of nuclei.
cytokinesis in animal cell by
formation of a furrow
cytokinesis in plant cell by
formation of cell plate
significance of mitosis?
1) Growth
2) Maintenance of cell size
3) Maintenance of chromosome number (genetic stability)
4) Repair
5) Reproduction
6) Healing & Regeneration
number of mitotic divisions required for formation of number of cells is
n - 1
number of generations (n) of mitosis for producing ‘x’ cells is
x = 2^n
the term meiosis was coined by
Farmer and Moore (1905)
in meiosis a single daughter cell forms -
4 daughter cells
