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Biology Module 2 > Cell division, Cell diversity and Cell differentiation > Flashcards

Cell division, Cell diversity and Cell differentiation Flashcards

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1
Q

What is cytokinesis

A

cytoplasmic division following nuclear division resulting in two new daughter cells

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2
Q

What is interphase

A

phase of the cell cycle where the cell is not dividing, it is subdivided into growth and synthesis phases

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3
Q

What is mitosis

A

type of nuclear division that produced daughter cells genetically identical to each other and the parent cell it maintains the chromosome number therefore the new cells contain the same genetic information

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4
Q

How do cells reproduce basically

A

they reproduce by duplicating their contents and then splitting into two daughter cells

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5
Q

what is m phase

A

this is only a small part of the cell cycle where nuclear and cytoplasmic division happens

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6
Q

What happens between Mo phase

A

interphase - this is where preparations are made for cell division in carefully ordered and controlled sequences with checkpoints

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7
Q

What are the two main checkpoints

A

the G1/sS checkpoint this is also called the restriction point
G2/M checkpoint
- there are other checkpoints such as one halfway through mitosis and one early in G1

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8
Q

What are the purpose of the checkpoints

A
  • to prevent uncontrolled division that would lead to tumours and cancer
  • to detect and repair damage to DNA - damage caused by UV light
  • so that they can ensure that the cell cycle cannot be reversed
  • so they can ensure that DNA is only duplicated once during each cell cycle
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9
Q

Phase of the cell cycle and checkpoints:

M phase

A
  • checkpoint triggers condensation of chromatin

- halfway through the cell cycle the metaphase checkpoints ensure that the cell is ready to complete mitosis

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10
Q

Events that happen within the cell: M phase

A
  • cell growth stops
  • nuclear division
  • cytokinesis
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11
Q

Phase of the cell cycle and checkpoints:

Gap phase 0

A
  • resting phase triggered during early G1 at the restriction checkpoint by a checkpoint chemical
  • some cells such as epithelial cells do not have this phase
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12
Q

Events that happen within the cell: Gap phase 0

A
  • may undergo go apoptosis, differentiation or senescence

- some types of cells such as neurones remain in this phase for a long time or indefinitely

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13
Q

Phase of the cell cycle and checkpoints: Gap Phase 1

A
  • a G1 checkpoint control mechanism ensures that the cell is ready to enter the S phase and begin DNA synthesis
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14
Q

Events that happen within the cell: Gap Phase 1

A
  • cells grow and increase in size
  • transcription of genes to make RNA occurs
  • Organelles duplicate
  • Biosynthesis, e.g. protein synthesis and making the enzymes needed for DNA replication in the S phase
  • p53, the tumour suppressor gene helps control this phase
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15
Q

Phase of the cell cycle and checkpoints: S phase of interphase

A
  • the chromosomes are unwound and the DNA is diffuse
  • every molecule of DNA is replicated, specific sequence to the replication of genes
  • genes that are active in all types of cells are duplicated first
  • genes that are normally inactive in specific types of cells are replicated last
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16
Q

Events that happen within the cell: S phase

A
  • once the cell has entered this phase it is committed to completing the cell cycle
  • DNA replicated
  • when all chromosomes have been duplicated each one consists of a pair of identical chromatids
  • rapid as the exposed DNA pairs are more susceptible to mutagenic agents this reduces the chances of spontaneous mutations happening
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17
Q

Phase of the cell cycle and checkpoints: Gap phase 2

A
  • special chemicals ensure that the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of the spindle
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18
Q

Events that happen within the cell: Gap Phase 2

A
  • cells grow
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19
Q

What are the steps in the cell cycle

A
  • M phase
  • Gap phase 0
  • Gap phase 1
  • S phase
  • Gap phase 2
20
Q

What are chromatids

A

replicates of chromosomes

21
Q

Why do all living cells need to produce genetically identical cells

A
  • Asexual reproduction - single celled amoeba and paramecium divide my mitosis to produce new individuals, some plants also, rarer in animals but some female harks kept in cavity without any males have to produce female offspring that are genetically identical to themselves
  • Growth - all multicellular organism grow by producing more cells that are genetically identical to each other and the parent cell
  • Tissue repair - wounds heal when growth factors secreted by platelets and macrophages and damaged cells of the blood vessel walls stimulate the proliferation of endothelial and smooth muscle cells to repair damaged blood vessels
22
Q

What are the main stages of mitosis

A
  • Prophase
  • metaphase
  • anaphase
  • telophase
23
Q

DRAW A PICTURE OF PROPHASE

A

DRAW IT

24
Q

DRAW A PICTURE OF METAPHASE

A

DRAW IT

25
Q

DRAW A PICTURE OF ANAPHASE

A

DRAW IT

26
Q

DRAW A PICTURE OF TELOPHASE

A

DRAW IT

27
Q

Describe the events in prophase

A
  • chromosomes that have replicated in the S phase of interphase consist of two identical sister chromatids which now shorten and thicken as the DNA supercoils
  • the nuclear envelope breaks down
  • the centriole in animal cells divides and two new daughter centrioles move to opposite ends of the cell
  • cytoskeleton protein tubulin threads form a spindle between the centrioles, the spindle has a 3D structure and is like lines of longitude on a virtual globe, in plant cells the tubulin threads are formed from the cytoplasm
28
Q

Describe the events in metaphase

A
  • the pair of chromatids attach to the spindle threads at the equator region
  • attach by there centromeres
29
Q

Describe the events in anaphase

A
  • the centromere of each pair of chromatids split
  • motor proteins walk along the tubulin threads and pull each sister chromatid of a pair in opposite directions towards opposite poles
  • because the centromere goes first the chromatids now called chromosomes assume a V shape
30
Q

Describe the events in telophase

A
  • separated chromosomes reach the poles
  • new nuclear envelope forms around each set of chromosomes
  • the cell now contains two nuclei each genetically identical to each other and to the parent cell from which they arose
31
Q

Describe how cytokinesis happens

A
  • in animal cells the plasma membrane folds inwards and nips in the cytoplasm
  • in plant cells an end plate forms where the equator of the spindle was and new plasma membrane and cellulose cell wall material are laid down on either side and along this end plate
  • two new daughter cells are formed that are genetically identical to each other and the parent cell
32
Q

What is a haploid

A

having only one set of chromosomes which is represented by the symbol “n”

33
Q

What are homologous chromosomes

A

matching chromosomes containing the same genes at the same places, may contain different alleles for some of the genes

34
Q

What is meiosis

A

type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell

35
Q

why does sexual reproduction increase genetic variation

A

because it involves the combining of genetic material from two unrelated individuals of the same species, by the process of fertilisation

36
Q

What does genetic variation do within a population

A

increases its chance of survival when the environment changes
- some individuals will have characteristics that enable them to be better adapted for the environment and enable them to change

37
Q

What needs to happen for sexual reproduction to occur

A
  • meiosis
  • in many organisms the body cells are diploid, for sexual reproduction to occur they must produce haploid gametes so that when two gamete nuclei fuse during fertilisation a diploid zygote is produced and the normal chromosome number is maintained
38
Q

What are the main stages of meiosis

A
  • two divisions in meiosis and in each division there are fours stages
  • in first meiotic division the four stages are prophase 1, metaphase 1, anaphase 1 and telophase 1
  • the cell then enters a short interphase before going to the second meiotic division
  • these are prophase 2, metaphase 2, anaphase 2, telophase 2
  • this takes place in a plane at right angles to meiosis 1
  • at the end of the second division cytokinesis may occur
39
Q

What happens in prophase 1

A
  • chromatin condenses
  • each chromosome supercoils
  • nuclear envelope breaks down and spindle threads of tubulin from form from the centrioles
  • the chromosomes come together in homologous pairs
  • each member consist of two sister chromatids
  • crossing over occurs where non sister chromatids wrap around each other and swap sections so that alleles are shuffled
40
Q

what happens in metaphase 1

A
  • pairs of homologous chromosomes I there crossed over state attach along the equator of the spindle
  • they attach to the spindle thread by its centromere
  • the homologous pairs are arranged randomly wit members of each pair facing opposite poles of the cell this is independent assortment
  • the way they line up here determines how they will segregate independently when pulled apart during anaphase
41
Q

what happens in anaphase 1

A
  • the members of each pair of homologous chromosomes are pulled apart by motor proteins these drag them along the tubulin threads of the spindle
  • centromeres do not divide and each chromosomes consists of two chromatids
  • the crossed over areas separate from each other, this results in the swapped areas of chromosome and allele shuffling
42
Q

what happens in telophase 1

A
  • in most animal cells two new nuclear envelopes form around each set of chromosomes, cell divides by cytokinesis, there is then a short interphase when the chromosomes uncoil
  • each new nucleus contains half the original number of chromosomes but each chromosome consist of two chromatids
  • in plant cells the cell goes straight from anaphase 1 into prophase 2
43
Q

What happens in prophase 2

A
  • if the nuclear envelope has reformed then they now break down
  • the chromosomes coil and condense each one consisting of two chromatids
  • the chromatids of each chromosome are no longer identical due to crossing over in prophase 1
  • spindles form
44
Q

What happens in metaphase 2

A
  • the chromosomes attach by their centromere to the equator of the spindle
  • the chromatids of each chromosome are randomly arranged
  • the way they arrange will determine how the chromatid separate during anaphase
45
Q

What happens in anaphase 2

A
  • centromeres divide
  • the chromatids of each chromosome are pulled apart by motor proteins that drag them along the tubulin threads of the spindle towards the opposite poles
  • the chromatids are therefore randomly segregated
46
Q

What happens in telophase 2

A
  • nuclear envelopes for around each of the four haploid nuclei
  • in animals the two cells now divide to giver four haploid cells
    in plants a tetrad of four haploid cells is formed
47
Q

How does meiosis produce genetic variation

A
  • crossing over during prophase 1 shuffles alleles
  • independent assortment of chromosomes in anaphase 1 leads to random distribution of maternal and paternal chromosomes of each pair
  • independent assortment of chromatids in anaphase 2 leads to further random distribution of genetic material
  • haploid gametes are produced which can undergo random fusion with gametes derived from another organism of the same species

Biology Module 2 (17 decks)

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