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Bio Rev > Chapter 6 Cell Cyle > Flashcards

Chapter 6 Cell Cyle Flashcards

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Biology 101 flashcards
1
Q

What is the fuel cyeof esnd three staged

A

Cell cycle is the ordered seauence of events in which a cell grows and divides it not two genetically id ecigls daughter cells

Invoked

Interphase
Mitosis
Cytokinesis

This is mitoitic division

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2
Q

What is interohade split it on

A

G1
S
G2

Can enter g0 after g1

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3
Q

What is interphase sbout

A

Long periods of growth and cell soends most of cycle here

Preparation for divisor.
But normal functions like respirwiton still carried out q

Referred as resting less,e not true, so many replicstion enxymes hormones etc all fine and prepare for celldivisoj very much active s

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4
Q

What happens in G1

A

First growth phase

  • proteins to make organelles are synthesised
  • all organelles REPLICATE including MITOCHONDRIA AND CHLOROPLASTS
  • cell increases in size
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5
Q

G2 phase?

A

Second growth phase

  • continues to increase in size
  • energy stores atp increase
  • proteins for cell division including enxymes etc are made

Energy needed to divide

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6
Q

But there are checkpojntd

A

G1 , G1 checkpoint, s , g2 g2 checkPoint

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7
Q

Checks in interphase what happens along with summary

A

G1

  • cell increase in size
  • proteins to make orgsnelles made, all organelles duplicated

G1 CHECKPOINT

  • checks for cell size, nutrient growth and DNA DAMAGE , if there then fix,
  • also ensures proteins needed for DNA replication there like helicase and polymerase , ligase

S
- replicate

G2

  • Grows in size again
  • increase energy store
  • checks for damages
G2 checkpoint 
# checks if DNA REPLICATED PROPERLY 
- any damage to dna and replicated 
- fixes 
- checks for cell size
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8
Q

Okay again g1 checkpoint snd g2 , what happens if not enter g1

A

If g1 checkpoint checks for nutrients, cell size, correct dna
If not ready, enter G0 PHASE WHICH IS PERMANENT REDTING

G2 ohase checks for cell size, enough energy store and that dna replicated correctly
If not it doedntgo into mitosis

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9
Q

G1

A

G1 increases size organllesduplicate, and SNSURES ALL PORTEINS LIKE ENZYMES NEEDED FOR REPLICSTION THERE

G2 GROWS MORR INCREASE ENERGY STORED AND CHECK DNA BROKEN

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10
Q

What is g0

Why do they enter

A

The ohase where cell leaves cycle either tmrlosrisky or oemensnlty . Hsppens after failing g1 phase at g1 checkpoint

Two reasons

1) if a cell has differentiated, it will permanelty be in this ohase, as a a cell thst has differentiated can no longer divide and enter cell cycle
2) if dna has been damaged it is no longer viable and can’t divide , this happens in checkpoint
- here a normal cell can only divide a few times before it has too much damage and becomes SENESCENT

being senescent = the inibauktu to divide , and as you grow older to number of these cells increase and this is linked with disease

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11
Q

Some cells come bac’?

A

Some cells can return to the cell cycle and divide like lymphocytes snd liver cells

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12
Q

Mitosis

A

Refers to division of the NUCLEI, once this happens (in telophase) mitosis complete. The division of cells is chrimones

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13
Q

When does mitosis happen (3)q

A
  • For growth
  • repairing of TISSUE
  • replacement of cells

In all eukaryotic organisms

It can also do asexual reproduction where one parent produces two genetically idnctislmofrpsrijt

Bacteria however DONT HAVE A NUCKEUD SO MITOSIS CSNT TSKE PLSCE, THEY DIVIDE BY BINARRY FISSION

So again for growth , replacement of cells and repair of whole tissues , happens in all eurksytotif snd sseduka reldiuction not in bacteriaq

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14
Q

State of DNA Before mitosis

A

DNA has been replicated in s ohase of interphase
- each new dna chromosome molecules is converted into to two chromstids

These wre held at religion called centromere which is middle
- this needs to happen so that they can be precisely manoevoured snd segregated equally

Again

In interphase dna combined with his tone proteins to make long thin molecule called chirmstim which is loosely coiled snd csnt see under micro joe
2) these finger into two strands called chromstids in middle joined st centromere , and this is two fhromsomes?

Two adjectives chromstids are sister chromstids of same chromosomes

Must be held in the middle so they can be segregstedn

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15
Q

State of dna before mitosis

A

DNA has just been replicated
- now dna combines with histone proteins to become chromatin, this is loosely coiled and csntbe seen under a microscope , and then this assembled as chomrstifes , two per chromosome at the centromere, which is needed so they can be mankuveured snd segregated easily

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16
Q

Early prophase

A
  • chromatin fibres begin to coil and condense to show as chromosomes= now you can see it under a microscope as it takes in any stain
  • nucleolus disappears (responsible for RNA synthesis) , and nuclear membrane begins to break down so that chromosomes are free in cytoplasm
  • here spindle fibre begin to be made and centrioles move to opposite ends

Again

  • chromatin begins to condense (means can take stain and seen on microscope)
  • nucleolus diss appear
  • nuclear membrwne begins to break down
  • spindle fibre begins to be made and centrioles move
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17
Q

What hat happens in late prophase / pre metaphase

A
  • centrosome of two centrioles are at oppsitepoles and now SPINDLE FIBRE INVADE NUCLEAR AREA, ATTACHING AT CENTROMERE AND BEGINNING TO PULL
  • by the end of prophase, the nuclewr membrane fully didentagrated
  • and chromosomes fully condensed

So essneitally in prophase

  • chromatin condenses to chromosomes , can take up stain and shown on microscope
  • nuecloelsu dissaoersm
  • nuclear membrane start to disintegrate
  • then the centrioles move to oppsiteends of cells, where mitotic spindle fibre invades nuckewrarea at the centromere
  • now membrwne fully gone and chromatin full chromosomes
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18
Q

Metaphase

THEN WHAT HAPPENS AND WHY IMPORTANT

A

Chromosomes pulled by spindle fibre are positioned along the metaphase plate , WITH CENTROMERES AT THE CENTRE

  • now SPINDLE FIBRE ASSEMBLY CHECKPOINT HAPPENS, this is where it is checked thst all the spindle fibre ha s been attached to the centromeres correctly, snd if not it haooend, this very importsnt because if incorrevtkybattached , then there could be an uneven distribution of chrome ones in resulting cells, and this leads to complications
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19
Q

Anaphase?

A

In anaphase ,

  • First the CENTROMERES DIVIDE
  • this allows spindle fibres to pull on divided centromeres and CONTRACT
  • thus sister chromatids are pulled to opposite sides, and cheomdomesnow on. Oth ends

Centromeres divide
Then spindle fibre pulls on divided, bringing sister components to opposite sides

20
Q

Telophase

A

Chromatids sister wre now known as separate chromosomes fully at opsotie ends ,
- now new nuclear envelopes fork around them so nucleolus os made

As two nuclei have now been successful,y divided to two, this makes the end of Mitleid, and the lhyscisl difidon next is mtidodi again
- chromsomesstart to uncoil

Telophase Gaian
- now sister chromaiatds chromsomed
- nuclear envelope begins to reform , so nucleus made again
# chromosomes begin to uncontested again and show as Chor sign lol

Mitosis complete

21
Q

What happens in mitosis fully

A

Prophase

  • chromatin molecules condense to become chromosomes, this means they can twke in stain and visible
  • nucleolus disappears
  • nuckewr membrwne envelope begins to disentragrate
  • centrioles move to ooosiite poles and start a making spindle fibre
  • spindlfe fibre invaded nuclear area, attaching to each centromere and begins to move them
  • nuclear membrwne fully disentagrwted

Metaphase

  • spindle fibres move chromsoesto the metaphase plat
  • SPINDLE FIBRE ASSMEBLY CHECKPOINT HAPPENS, here it checks each chdormomed has been attached to spindle fibre coorecrtly, importsnt because if not, when contracting there will be an uneven distribution of chromosomes and lead to problem

Anaphase
- here centromeres each divide, and spindle fibre contract on each splitter centromere, bringing sister chromatids to each pole

Telophase
- now each sister chromatin is now a chromomosome ,
- nuclear membrwne begins to reform and nucleolus returns
X and chromosomes uncoil again to become chromatin again
# now division fo nuclei succes and mitosis completed

22
Q

Cytokinesis in animals.

A 
- cleavage furrow domes around the middle of the cell 
# the cell surface me,brwne is lulled inwards by the cytoskeleton until it is close enough to fuse around the middle forming two cells
  • cleavage Furors forks around the middle
  • cell surface membrwne is pulled inwards by cytoskeleton until it is close enough to fuse around the middle forming two cells

Cleavage furrow middle
- cytoskeleton pukks membrwne in wards until tie close enough to fuse wnd before separate cells

23
Q

How does cytokinesis happen in plants cells?

Why is it different to animals ?

A

Plant cells have a CELL WALLA SO NIT POSSIBLE FOR CLEAVAGE FURROW TO HAPPEN
so vesicles from Golgi apparatus being to asdemble in the ewme llace where metaphase plate was
£ and they fuse with each other AND the plasma membrane , which divides them into to two

  • now new sections of cell wall fork along the new sections of membrwne

Here the cell wall has to fork AFTER THE CELLS DIVIDE, otherwise they would undergo osmotic lysis from sore undoing area

24
Q

Recap of both chtokineiss

A

Animal
- cleaver furrow forms in the middle, where cytoskeleton pulls the cell surface emmrbwne inwards until the membrwne can fuse, which creates two cells

Pkanrs

  • due to cell walls a cleavage furro csn’t form
  • thus vesicles from glkiti apparatus aggregated same place where metaphase plat is
  • they fuse and with the membrwne , and this causes cell to divide
  • after division cell wall made, if happened before cells would undergo lysis almost straight away!
25
Q

How to investigate and see mitosis using root cells?

A

1) trat them with hydrochloride acid
2) then sprewd them apart, stain and squausn
View

The reason why you use root cells is because they are a source of Kerri Dirk tissue, snd it is this tissue which is able to undergo mitosis in plants only

Use plants too because they are very easy ti source and easy to observe too

26
Q

What is sexual reproduction

A

It is when two sex cells, gametes, one from Esch parent fuse to form a fertilster egg which is a zyogeote, this then divides by mitosis to form other cells which differ Jetset

Here each gamete must be haploid so resulting xygote is diploid

Sexual reproduction

Where two sex cells gametes fuse from Esch parent to make a zygote, and this then divides by mitosis to form an embryo where cells develop from there, where they are all haploid

27
Q

What is difference between normal body cells and gamete? What are normal body cells

A

Normal body cells contain two versions of each chromosomes , called homologous chrondomes, this means

  • has same type of gene , but not same
  • this gene is found at the same Loci in homologous chromosomes
  • and same size too

This makes bidy cells 2n

As gametes must fuse to produce a bidy cell they must have half the number of chow o Ed and so n

This happens by meiosis

So homologous chromosomes of each bidy cell
= same size, same type of genes and same loci

28
Q

Why is meiosis considered REDUCTION DIVISION

A

This is bevause each daughter cell contains HALF THE NUMBER OF CHROMOSOMES OF ITS PARENT CELL, so it has reduced the number of chormdoked do reduction

Here 2; to 2; to n

Mitosis produced two genetically,y identical 2n to 2n so not llmelsises genetically different 4 and so reduction division

29
Q

Alleles what are they?

Centromeres?

A

An allele is just a different version of the same gene, and all these genes will have the same LOCI ON THR HOMOLOGIUS CHROMSOKES

As homologous chromosomes have the same genee in the same position, it will habe the same Length snd size too

What about centromere? The centromeres will be at SAME POSTION RELATIVELY TOO

So homologous again
- have same type of eigene in same loci but also same size and Knetgummis when visible. And they are visible at the end of prophase

30
Q

What happens before meiosis too, simialr to mitosis? Describe

A

Interphase happens, and by the. The dna has duplicated, where it has combined with histones proteins to make chromatin , and arranged itself as two molefukes of chromatische for a chromosome, as sister chrinatids

31
Q

So before meiosis is

A

Again interphase, with dna duplicating and combining with histone proteinsto form chromatin , arranging in molecules of chrosmtids where two sister cimrtsidd make one shcomeokse, held at the centromere ,

32
Q

Mesons is 1 !

A

Is reduction division, because each cell goes from having 2 sets of chromosomes to one, and meiosis 2 it is one to one

33
Q

What happens in prophase 1

A
  • chromosomes condense again to form chromosomes that can take up stain
  • nuckeolus dissapear
  • nuclear membrane disentagrste
    Spindle fibre still is made with centrioles moving to oppsite poles and being made ,
    BUT NOW
  • HOMOLOGOUS CHEODMOMES (so one one from each side ) actually pair up
  • this forms bivalents and results in cross over and change of genetic information lewdifjt I variation when broken later
34
Q

So you now know in prophase 1 , as well as ebehrhting old, homologous chromsokespair up and form bivalsnrts but what even are these

A

These are what you call them when the homologous chromates ENTANGLE , leading to crossover over of genetic information

Here wherever crossover chiasma is formed

Then genetic infirmstjon seithc over when snoohsse happens and they dolit apart

35
Q

Okay what about metslhase 1

What is the effect of thid ?

A

Same as mitosis, spindle fibre invade ncukewr area and bring chromosomes to the metaphase plate in line, but this time , the HOMOLOGOUS LAIRS LINE UP IN THE MIDDLE AS PAIRS (before it didn’t matter, could’ve been straight )

The ORIENTATION OF THE CHROMOMES Is not determined whether the duplicated male ones face the pole or female is not known

This is known as INDEPENDENT ASSORTMENT ! And this leads to many combinations of proprtion if male chromsimedor female ending in the cell

This leads to genetic variation

Okay so same thing, spindle fibre invade and brings chromosomes to metaphase plate, but this time sssembled the homologous pairs next to each other

This leads to idneodent assortment, here the way the partenal or maternal duokcuster pair face is not determined by anything, as a result kesdsto many combinations of proportions going into cell and thus GENETIC VARISTION

36
Q

Anaphase 1

A

Here in anaphase 1, it is different to mitosis in the sense yes the soindke fibre contracts , but here the CENTROMERES DONT DIVIDE, AND THE SISTER CHROMSTIDD STAY INTACT this time

What happens is when the centromere are pulled, where the chromstids of the bivkanrt were tangled , chi Asmara , break and rejoin , forming RECOMBINANT CHROMATIDS

This leads to an exchange of dna and leads to more combinations of alleles on the new chromosomes than what it was before = this leads to even more genetic variation

What happenstance

Same = spindle fibre contract at the centromeres, but this time the sister chromstids aren’t pulled apart but still intact, instead the whole chromes is pulled to a side.

However where they were entangled at the chainsaws break off and rejoin, to form recombinant chromstids. This was an exchange of dna and genes, leading to new combinations if genes on the chromosomes than it was before, snd thus lesfing to more genetic varaitin

37
Q

Telophase 1 and cytokinesis

A

Essentially the same
- now chromosomes uncoil and become chromatin again, nuekcear membrane reforms and nuclolud there, split of the nuclei, and cleavage furrow cytoskeleton pulls in and causes fuse, and two cells are now made

Here each whole thing is known as a chromsome

As a result you went from 2n to n, and reduction divisio is complete, diploid to haploid

Again , same thing , and reduction division comokinrwrty now as one whole thing s chrodmomed

38
Q

What happens in prophase 2

A

Exact same as mitosis l
- chromatin condense and visible
- nucleolus disappear, nuclear membrane dusentagrsteb
Centruoles move to opositesides and spindle fibre begins to be made

39
Q

Metahosee 2

A

Now again spindle fibre invade and bring to the metaphase plate

  • but now each chromstids is different, and once again the direction they face is undetermined
  • so again we have a case of INDEPENDENT ASSORTMENT , where due to the direction they face even more combination ifthe recombinant chromstids end up is countless and so genetic variation indreases here just like metaphase 1

BUT no crossover

40
Q

Anaphase 2

A

This ripen not crossover happens, and actually centromere divide and chromstids, unlike anaphase 1 ahre plukled to bith ends and pulled apart when contracted

41
Q

Telophase 2

Cytokineisns

A

Same thing , chromosome uncoil and nucleolus apparsr, nuclear membrsne reformed again

Agains cleavage Bruno, cytoskeleton pull on plasma membrane until fuse and solit

Tpfinsk product = haploid cells due to reduction division st the start, from 2n to n, here you went fork no to n , with 4 genetically different fhromsoked

42
Q

Okay so where did 3 poitne of genetic vsifsjtinniccur

A

1st at prophase 1, when they line up together as homologous chromosomes, bivskents are created, where parts of chromstids from the homologous chrosmomose entangle with each other at the chiasmats. When thidnid pulled slsrt in anaphase they will break and rejoin and form recombinant chromstids, and here transfer if dna lesds to more combinations of different genes in the chronsomesleading to genetic variation

2) metaphase 1, when line at plate, random assortment direction face not determiend such that when they are pulled apart, the proportions of paternal and maternal going to each cell id not the same and again leads to more comibinsittions of overall chromosomes and genetic info

Against in metaphase 2,

43
Q

Main difference of meiosis to mitosis

A

1) prophase kine up as homologous chrosmomeus
2) metaphase 1 line up as homologous chromosomes at metaphase plate
3) anaphase 1 chromstids still intact, centromere pulled and this is reduction division

Random assortment

Prophase 1 same, metaphase 2 again random asdirtment but the thin thag ssme

44
Q

How to say

A

So when entangled snd break off, leads to genetic variation due tie SHC age of dna and now chromosomes will have different combinations if alleles then before

When independent addortment , the total combination if chromosome swill be different too leading to genetic version

45
Q

How to ibserve meiosis?

A

Use anthers of plant

Then put into a slide and isbere

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