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Cell cycle and cell division Flashcards

1
Q

RBC and WBc is formed by

A

cell diffrentiation of haemopoetic stem cell

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2
Q

Why DNA replication is a discontinuous process?

A

because it takes place only in S phase

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3
Q

Is cell growth [cytoplasmic] continous or discontinuous ?

A

continuous as it takes place in the entire cycle

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4
Q

what is genome ?

A

total DNA present in haploid set of chromosome

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5
Q

what is the amount of genome in G1 phase ?

A

n/c

n= number of chromosome 
c= amount of dna
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6
Q

what ids the amount of DNA in s phase ?

A

n/2c

n= number of chromosomes 
c= amount of dna
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7
Q

What is significant about S phase ?

A

number of chromatin [chromosome] doesn’t change but amount of DNA [genome] doubles

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8
Q

what is the duration of cell cycle in E.coli , yeast and human cell

A

2o minutes ,
90 minutes,
24 hours

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9
Q

cell cycle is regulated by

A

cyclin protein and CDK enzyme [ cyclin dependant kinase ]

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10
Q

what is the decreasing order of duration of various phases of cell cycle in human cell ?

A

G1 > S > G2 > Prophase > Metaphase > Telophase > Anaphase

10h >9h>4h > 1h

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11
Q

which is the most dramatic phase of cell cycle ?

A

M phase because it involves reorganisation of almost all cell organelles

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12
Q

Which phase is metabolically most active ?

A

interphase

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13
Q

what is the variation of g1 phase ?

A

G1 phase is short in frequently dividing cells and vice versa

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14
Q

Significance of Sphase

A 
duplication of centrosomes 
synthesis of histone protein
synthesis of kinetochore subunits 
dna replication
genome doubles but number of chromosomes remains same
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15
Q

significance of G2 phase

A

tubulin protein synthesis

increase in number of cell organelles

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16
Q

what is the difference between quiescent phase and senescent phase ?

A

quienscent phase = due to lack of mitogen[chemicals that induce cell division] or ATP
senescent phase = after a number of rounds of cell division due to decreased telomerase activity

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17
Q

when does DNA replication take place in prokaryotes

A

DNA replicates before binary fission and not in S phase ‘EXCEPTION’

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18
Q

term mitosis was coined by

A

Walter Fleming

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19
Q

Who discovered mitosis in animal cell and plant cell ?

A

Walter Fleming

Strasburger

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20
Q

does mitosis take place in animal germ cell

A

yes , in undifferentiated animal germ cell

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21
Q

what is the major difference between mitosis and meiosis ?

A

in mitosis the parent cell and daughter cell are genetically identical as no crossing over takes place

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22
Q

formulas related to generation time

A

number of mitosis required = X-1
number of mitotic generation required = 2^n= X

where X = number of cells and n = number of generation

23
Q

what are the main features of early prophase

A

condensation of chromatin into chromosomes by condensin protein
chromatids are not visible
also called spireme stage
chromosomes appear longest and thinnest

24
Q

features of middle prophase

A

chromatids become visible

nuclear membrane starts dissapearing

25
Q

what are the constituents of mitotic apparatus

A

spindle fibres + 2 asters

26
Q

metaphase is marked by

A

complete disappearance of nuclear memberane and complete condensation of chromosomes

chromosomes are thickest and shortest
best phase to study and visualize the chromosomes
congression takes place
formation of equitorail plate

27
Q

what is congression ?

A

the process in which spindle fibres bring chromosomes at equator of spindle [ formation of metaphasic plate ]

28
Q

How does the onset of anaphase takes place ?

A

MRF activates APC inactivates Anaphase inhibitors

MRF [ Maturation promoting factor ]
APC [ anaphase promoting complex ]
anaphase inhinbitor example - securin

29
Q

what happens in anaphase ?

A

splitting of centromese and breakdown of cohesion protein and then sister shromatids become free and now called daughter chromosomes

30
Q

______plant cell spindle fibres _________

A

interzonal

persists even after telophase

31
Q

centromere , centriole and centrosome

A

centromere id present in the chromosome where kinetochore is present

centrioles are cylindrical and 2 form centrosome

centrosomes form equitorial pate by spindle fibres and help in congression

32
Q

cytokinesis facts

A

normally starts afyer the completion of karyokinesis but in some cases starts in anaphase and ends by telophase

in animal cell contractile ring deepns to form furrow

in pant cell furrow cant be formed because of the cell wall so cell plate is formed by fusion of golgian vesicles

cell plate represents middle lamella and precursor of cell wall formation

cell furrow grows centripetally

cell plate grows centrifugally

33
Q

what is synctium

A

karyokinesis without cytokinesis leads to multinucleate condition called synctium
e.g. liquid endosperm in coconut

34
Q

what are the two conditions for better metabolism ?

A

high surface area / volume ratio
high N/c ratio

[ mitosis hepls to increase metabolism ]

35
Q

difference between mitosis and meiosis

A

mitoisis- one round of dna replication ; one round of separation ; one round of nuclear division

meiosis - one round of dna replication ; 2 rounds of separation ; 2 rounds of nuclear division

36
Q

what is the condition for n/c ratio for meiocyte ?

A

can only be even like 2n 4n 6n ……. etc

37
Q

What are the three types of meiosis

A

1) gametic meiosis- end product is gamete and it occurs in diplontic organisms like animals, angiosperm, gymnosperm
2) sporic meiosis - end product is a spore and occurs in haplodiplontic organisms like bryophytrs and pteridophytes
3) zygotic meiosis - takes place in zygote in haplontic organisms like most of algae

38
Q

Which prophase of all is longer and mire complex

A

Prophase 1

39
Q

Leptotene is also called

A

Bouquet stage

40
Q

What is synapsis and when does it takes place

A

Synapsis is the pairing of homologous chromosome by synaptonymal complex forming a bivalent or a tetrad

It takes place in zygotene

41
Q

When does the crossing over takes place

A

Pachytene

42
Q

Crossing over is mediated by

A

Recombination nodule which has recombinase enzyme

Along with endonuclease and ligase

43
Q

Chromatids become visible in which part of prophase 1

A

In pachytene

No. Of tetrads = No. Of bivalents = n ( 2n if meiocyte)

44
Q

Diplotene

A

Desynapsis

Chiasmata remains

Nuclear membrane and nucleus start disappearing

This phase is long in some vertebral oocytes and such long diplotene is called dictyotene phase

45
Q

Diakinesis

A

Terminalization of chiasmata

Inhibition of RNA synthesis

Nuclear membrane and nucleolus completely disappear

Centrosomes on opposite poles

Spindle fibre formation

46
Q

Centrosomes duplication occurs when in meiosis

A

During interkinesis

47
Q

How many metaphasic plates are formed in metaphase 1

A

2

48
Q

Why meiosis is called reductional division

A

Number if chromosome gets reduced

Only meiosis 1 is reductional but meiosis 2 is equational

49
Q

What is a mitogen

A

Promotes cell division like auxin, cytokinin, gibberlin, patelet growth factor, lymphokinase, insulin

50
Q

Colchicine is obtained from

A

Colchicum autumnale (Liliaceae)

51
Q

Which mitotic poison inhibits polymerisation of spindle fibres

A

Cilchicine

52
Q

Which poison inhibits cell cycle at interphase

A

Ribonuclease and cyanide( inhibits atp formation)

53
Q

What is the n/c ratio in angiosperm’s endosperm?

A

3n/3c

wrong answers (5 decks)

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