Cell division notes du, Study notes of Biology

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Cell

Cycle

E

Division

Phases (^) of cell^ cycle

mitosis

meiosis

Qts

Phases of cell (^) Cycle

During

division

of cell (^) , DNA (^) replication and

cell

growth

takes (^) place. Cell cycle Sequence^ of^

events

by

which a

cell (^) duplicates its genome , synthesis the (^) other constituents of cell (^) and eventually

divides into

two

daughter

cells (^).

• The human cells^ divide^ once in^

approximately

24 hours (^).

• Yeast cell divides^ in^90 minutes^. Fritchman Phases (^) of cell^ Cycle

Pmt-

• INTERPHASE
• M^ phase (^) NEET - 2017 INTERPHASE

Resting phase

• cell (^) prepares (^) for division^ by undergoing both cell growth and DNA (^) Replication in^ an order (^).
• further Divided into.^ - (^) NEET - 2019

42 - Gap 's phase g

phase (synthesis)^

NEET- (^16) (Il) Gz-Gap 2 phase

• Interval^ between. DNA (^) replication in nucleus. Proteins^ are

mitosis & initiation (amount of DNA

synthesised

of DNA^ Replication^. chromosomedoubles^ but Nothe . remains

• Metabolically Active^ same) . Cell (^) growth
• Grows continuously

. Centriole^ duplication in continues

cytoplasm.

PROPHASE METAPHASE^ ANAPHASE^ TELOPHASE

• 1st (^) phase • complete dis -^ • Each^ chromosome.^ Final^ stage
• marked^ by integration^ of arranged^
• at when chromosomes

initiation (^) nuclear (^) envelope metaphase. plate at (^) holes de - of condensation^ marks^ its^ is^ split into^ condense^ and of chromosomal^ starting.^2 daughter lose their material (^). chromatids (^) , individuality.

• Centrosome^

Morphology of^ now^ referred as begins to^ chromosomes move towards observed^ -^ daughter^ completion chromosomes (^). marked By

' hole ' •• Daughter chrom - chromosomes completion (^) completion osomes move cluster at Marked By

• marked

by

towards (^) poles (^) opposite poles chromosomal

• spindle (^) fibres and identity is B (^) material centromere is (^) lost (^) as discrete condenses to attach^ to leading edge^ elements^.

form compact^

kinetochores

chromosomes (^) (disc^ shaped while (^) arms structures at trail behind (^).

as nuclear^ envelope

chromosomes surface of

Bo (^) seen to (^) be (^) chromosomes ) develops^ around composed (^) of PMT^ -^ u^ Completion chromosome^. (^2) chromatids (^) marked By

attached (^) at (^) - NEET-^ lb

centromere →^ nucleolus^ ,

og chromosomes^ centromere (^) Golgi complex , → Each^ centrosome^ moved to (^) spindle split and^ ER^ reform radiates out equator and^ chromatids microtubules (^). get (^) aligned separate and §g Do not show (^) along metaphase

move to

golgi bodies (^). ER plate (^) through. nucleolus (^) , nuclear opposite poles. spindle (^) fibres membrane to both (^) polls Two (^) asters t spindle (^) fibres = (^) Mitotic (^) Apparatus

pm

• w "

CYTOKINESIS

• Separation (^) of (^) cytoplasm
• (^) nimal cell (^) Plant cell (By cell^ furrow) (^) (

By cell^ plate)

• furrow^ appears in. This (^) different

hlasma membrane^. method^ is

because of presence

• furrow^ gradually of inextensible deepens and^ cell^ wall^. ultimately joins^ in centre (^) dividing.^ wall^ formation cytoplasm into starts in centre z

two . of cell and

grows outward to 0 to meet^ existing Diagram

-^ PMT - zero an (^) lateral walls. →

(^) (The^ formation of new^ cell^ wall H A begins^ with^ formation^ of simple precursor called^ cell^

plate which^ represents middle lamella) ¥ (^). In (^) some organisms : karyokinesis is in

not (^) followed by cytokinesis leading r to^ multinucleate^ condition^. N (^) (SYNCYTIUM)→ (^) Eg : liquid Endosperm E in^ coconut SIGNIFICANCE OF^ MITOSIS is (^).^ Growth^ of

multicellular

organisms (to^ restore^ nuclei^ - cytoplasmic ratio) (^2). cell (^) refrain father layer^ of^ epidermis, lining of^ gut ,^ Blood^ cells replace (^) continuously )

PRO PHASE -^ I

' Typically longer^ and more (^) complex when compared to^ prophase (^) of mitosis

(EP TO TE NE

• chromosomes (^) become gradually

visible .

• compaction of chromosome continues^. ZYGOTENE
• chromosomes^ start haining together ( SYNAPSIS)
• Such^ haired chromosomes^ are called^ homologous chromosomes (^).

Synapsis is^ accompanied^ by formation of

synaptonemal complex^.

• Complex formed by^ pair^ of^ synapsid^ homologous chromosomes called (^) as BIVALENT (^) / TETRAD^. PAC (^) HY TENE i
• Bivalents more clearly

visible .

• Long lived (^) compared to above (^2) stages
• 4 chromatids of

each bivalent^ becomes^ Distinct

and clearly visible (^) as TETRADS (^).

• Appearance (^) of Recombination^ modules^ (^ site^ at which crossing over occurs)
• Recombination is^ completed

by

end (^) of pachytene

leaving

chromosomes linked^ at^ site

of crossing over (^). - rhyme mediated (^) process ( enzyme Recombinase) PMT-^2012

Exchange of^ genetic

material between

2 homologous chromosomes (^).

DIPLO TEN E^ NE ET^ - 2018

Beginning of^ diplotene^ recognised^ by

dissolution of synaptonemal^ complex^.

• chromosomes^ separate except at^ site^ of crossing over which (^) are x - shaped structures called CHIASMA TA^. In oocytes of some vertebrates - Diplotene can last for months (^) or years DIAKINESIS
• Final^ stage of Prophase^ I (^).
• Marked^ by

Terminilisation

of

chiasmata

• Nucleolus (^) disappears (^) , nuclear^ envelope breaks (^).

It is transition to

metaphase I (^).

METAPHASE

• I
• Bivalent^ chromosomes^ align on (^) equatorial plate. .
• (^) Microtubes (^) from opposite poles^ of^ spindle

attach to kinetochore

of (^) homologous chromosomes (^). ANAPHASE

• (^) I

Homologous chromosomes (^) separate while^ sister

chromatids remain associated^ at^ centromeres

SIGNIFICANCE OF MEIOSIS

1. Conservation

of (^) specific chromosome^ No (^). of each (^) species is achieved (^) across

generations

in

severally reproducing organisms^

. (^2). Results in (^) reduction of chromosome No^.

by

half . (^3). Increases genetic variability in (^) population from one

generation

to another.

FORMULAS USED

• (^) No. of Mitotic Divisions (^) required for formation of

en '^ cells^ =^ n^ -^2

• (^) No.

of generations of^

mitosis (^) for fvueducing N no. of cells^ x - -^ 2n

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