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Cell cycle and cell division Flashcards

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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

Study These Flashcards
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

Study These Flashcards
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

Study These Flashcards
A

chromatids become visible

nuclear membrane starts dissapearing

25
what are the constituents of mitotic apparatus
spindle fibres + 2 asters
26
metaphase is marked by
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
what is congression ?
the process in which spindle fibres bring chromosomes at equator of spindle [ formation of metaphasic plate ]
28
How does the onset of anaphase takes place ?
MRF activates APC inactivates Anaphase inhibitors MRF [ Maturation promoting factor ] APC [ anaphase promoting complex ] anaphase inhinbitor example - securin
29
what happens in anaphase ?
splitting of centromese and breakdown of cohesion protein and then sister shromatids become free and now called daughter chromosomes
30
______plant cell spindle fibres _________
interzonal | persists even after telophase
31
centromere , centriole and centrosome
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
cytokinesis facts
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
what is synctium
karyokinesis without cytokinesis leads to multinucleate condition called synctium e.g. liquid endosperm in coconut
34
what are the two conditions for better metabolism ?
high surface area / volume ratio high N/c ratio [ mitosis hepls to increase metabolism ]
35
difference between mitosis and meiosis
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
what is the condition for n/c ratio for meiocyte ?
can only be even like 2n 4n 6n ....... etc
37
What are the three types of meiosis
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
Which prophase of all is longer and mire complex
Prophase 1
39
Leptotene is also called
Bouquet stage
40
What is synapsis and when does it takes place
Synapsis is the pairing of homologous chromosome by synaptonymal complex forming a bivalent or a tetrad It takes place in zygotene
41
When does the crossing over takes place
Pachytene
42
Crossing over is mediated by
Recombination nodule which has recombinase enzyme | Along with endonuclease and ligase
43
Chromatids become visible in which part of prophase 1
In pachytene No. Of tetrads = No. Of bivalents = n ( 2n if meiocyte)
44
Diplotene
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
Diakinesis
Terminalization of chiasmata Inhibition of RNA synthesis Nuclear membrane and nucleolus completely disappear Centrosomes on opposite poles Spindle fibre formation
46
Centrosomes duplication occurs when in meiosis
During interkinesis
47
How many metaphasic plates are formed in metaphase 1
2
48
Why meiosis is called reductional division
Number if chromosome gets reduced Only meiosis 1 is reductional but meiosis 2 is equational
49
What is a mitogen
Promotes cell division like auxin, cytokinin, gibberlin, patelet growth factor, lymphokinase, insulin
50
Colchicine is obtained from
Colchicum autumnale (Liliaceae)
51
Which mitotic poison inhibits polymerisation of spindle fibres
Cilchicine
52
Which poison inhibits cell cycle at interphase
Ribonuclease and cyanide( inhibits atp formation)
53
What is the n/c ratio in angiosperm's endosperm?
3n/3c

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