mitosis Flashcards

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1
Q

what is the series of events in which a cell is formed and divides into daughter cells called

A

the cell cycle

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2
Q

what are the 3 phases of the cell cycle

A

interphase - the longest
nuclear division - mitosis
cell divisison- cytokinesis

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3
Q

what is interphase

A

90% of cell cycle
cell is metabolically active

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4
Q

what is G1

A

intensive growth and activity
organelles - mitochondira golgi etc are produed
rRNA,mRNA,tRNA IS PRODUCED

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5
Q

What is the point at the end of G1 called

A

the restriction point

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6
Q

what is the role of tje restriction point

A

cells that pass are committed to completing the cell cycle many cells do not pass this point and remain in g1

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7
Q

what is S

A

synthesis
DNA is replicated by the semi-conservative method
chromosomes now consist of two identical molecules called chromatids- joined at the centromere

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8
Q

what is G2

A

period of cell synthesis -histones synthesised and spindle proteins are produced
DNA checking occurs

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9
Q

What is m phase

A

mitosis

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10
Q

what is cytokinesis

A

cell organelles + cytoplasm separated equally and cell divides into 2 daughter cells

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11
Q

description of mass graph

A

mass doubles (from given units in question) in 12 hours (or given hrs in q)
then mass havles from ‘’’ at ‘’ hrs

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12
Q

explanation of mass graph

A

from ‘’’ hrs cell undergoes growth,synthesis, DNA replication and nuclear divison
at ‘’ hrs the cell cycle is completed as the cell undergoes cytokinesis , forming 2 new daughter cellls

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13
Q

DNA graph D + E

A

d = FROM ‘’ HRS dna mass remains constant at ‘’ units
E= the cell is in G1 which is a period of cell growth and cell activity
d= the DNA mass doubles from ‘’-‘’ units in ‘’-‘’ hours
E= DNA is replicated by the semi-conservative method during the S phase, so at the end of the S phase each chromosome is now 2 chromatids
d= from ‘’-‘’ hrs DNA mass remains constant at ‘’ units
e= as the cell completes G2 and mitosis
d= DNA mass havles at ‘’ hrs from ‘’-‘’ units=
e= as the cells complete cytokinesis

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14
Q

what are the four stages of mitosis

A

prophase
metaphase
anaphase
telophase

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15
Q

what is the process of mitosis

A

it is a continuous process

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16
Q

what is prophase

A

-chromosomes condense - get fatter + shorter
this is bc the condense around histone proteins
-individual chromosomes are now seen as chromatids joined at the centromere
-the nucleolus disappears
-the the centriole migrate to the opposite ends of the cell
-spindle forms
-nuclear membrane breaks down and disappears

17
Q

what is metaphase

A

-chromatids become attached to the equator of the spindle by their centromeres

18
Q

what is anaphase

A

-the centromeres split and the chromatids split
-this is bc spindle fibres begin to pull apart
-each pair of sister chromatids separate and are pulled to opposite poles of the spindle

19
Q

what is telophase

A

-chromosomes at each end of the spindle decondense
-spindle fibres breakdown
-nuclear membrane forms around each of daughter nuclei
-nucleolus reappears

20
Q

what is cytokinesis

A

cell organelles are equally distributed bwt 2 ends of the cell
-animal - cell membrane invaginate at the equator of the cell - the cell then splits in 2
-plant-fibres bulge outwards to form barrel shaped called phragmoplast
-organelles gather and golgi produce many vesicles fuse and form a cell plate
new double membrane forms and the cell wall material deposited bwt membrane layers - cell in 2

21
Q

what is the significance of mitosis

A

-genetic stabilty- clone produced as the cells hab=ve same no. of chromosomes
-growth- cell tissue needs to be identical to the existing cels so they carry the same function
-repair- must replace damaged cells with exact copies of the original cell for the tissue to function produces
-asexual reproduction- produces offspring that is genetically identical to parent

22
Q

what does the mitotic index show

A

how much a tissue is actively dividing

23
Q

what is the mitotic index

A

no. of cells in mitosis/ total no. cells counted

24
Q

mitotic index example

A

cell cycle = 22 hrs
and mitotic index = 0.18
so mitosis takes 22 x 60 x 0.18 = 237.6 min

25
Q

what is cancer

A

uncontrolled cell division
form a tumour (an irregular mass of cells)

26
Q

how are cancers formed

A

Cancers start when changes occur in the genes that control cell division. A change in any gene is known as a mutation. If the mutated gene is one that causes cancer it is referred to as an oncogene

27
Q

how are cancers not developed more often

A

Mutations are common events and don’t lead to cancer most of the time
Most mutations either result in early cell death or result in the cell being destroyed by the body’s immune system
As most cells can be easily replaced, these events usually have no harmful effect on the body

28
Q

how do the mutations cause cancer

A

the mutations that result in the generation of cancerous cells do not result in early cell death or in the cell being destroyed by the body’s immune system
This means that the harmful mutation occurring in the original cell can be passed on to all that cell’s descendants
A typical tumour contains around a thousand million cancerous cells by the time it is detected

29
Q

what are carcinogens

A

Carcinogens are any agents that may cause cancer (eg. UV light, tar in tobacco smoke and X-rays). If the agent causes cancer it is described as carcinogenic

30
Q

what are the genes involved in controlled cell division

A

proto-oncogenes = stimulate cell division
tumor suppressor genes = inhibit cell division

31
Q

when does uncontrolled cell division occur

A

when the TS genes are off and the POG genes are on all the time

32
Q

how do prokaryotes divide

A

binary fission

33
Q

what is the process of binary fission

A

-dna in singular circle chromosomes copies by semi-conservative method
-each copy becomes attached to the CSM and the cell elongates
-the two copies separate - so each daughter cell receives one
-cell membrane invaginates and new cell wall material is laid down
-cross wall completed and two new daughter cells become separated
-2 daughter cells are genetically identical clones of each other and the original parent cell

34
Q

how do viruses replicate

A

-infect a host cell
-use host cell machinery to produce copies of the viral nucleic acid and proteins
-released from the host cell either by causing the host cell to burst or by budding from the host cell membrane

35
Q

how do bacteriophages replicate

A

-virus attaches to the bacterial host cell and injects the DNA into the cell
-the viral cell DBA is copied to make copies of the DNA and it is also transcribed and translated making new viral proteins
-new virus particles are then assembled and the host cell burst releasing new viral proteins

36
Q

how does HIV replicate

A

-virus attaches to specific receptor protein in the T-helper cells and the protein of the capsid of the virus fuses with the host cell membrane
-viral RNA and reverse transcriptase released into host cell
-reverse transcriptase makes a DNA copy of viral RNA
-DNA copy is integrated into t-helper cells own DNA
-DNA transcribed to RNA
-some of RNA is transcribed to vira; proteins and forms new genetic material of the virus particle
-new virus particles assembled and bud off from CSM