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Biology A Level > Mitosis > Flashcards

Mitosis Flashcards

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1
Q

How can a cell’s life be described?

A

A cells life can be described through a series of stages.

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2
Q

What are these stages known as?

A

Stages of a cell cycle

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3
Q

What do all multicellular organisms use the cell cycle to do?

A

The cell cycle is the process that all body cells from multicellular organisms use to grow and divide.

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4
Q

How many phases is the cell cycle divided into?

A

The cell cycle is divided into 2 phases:

  1. Interphase
  2. The M phase
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5
Q

How long does it take a cell in a human embryo to complete one cycle?

A

It takes about 24 hours

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6
Q

What percentage of the cell cycle is spent in interphase?

A

95%

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7
Q

How long does the M phase last?

A

About 30 minutes

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8
Q

What is the name of the first section of interphase?

A

G1 phase

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9
Q

What happens in G1?

A

Growth of cell
Growth of organelles
Organelles duplicate synthesis of proteins (e.g. Making enzymes for DNA replication)

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10
Q

What is the second section of interphase called?

A

S - synthesis phase

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11
Q

What does it mean in terms of the cell’s commitment to completion once its entered the S phase?

A

Once the cell has entered the S phase it is committed to completing the cell cycle

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12
Q

What happens in the S phase?

A

DNA REPLICATION

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13
Q

Why is the S phase so rapid?

A

The S phase is rapid because the exposed DNA bases are susceptible to mutagenic agents. The rapidness of the S phase reduces the chance of spontaneous mutations occurring.

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14
Q

What is the G2 phase?

A

The G2 phase is the second growth phase

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15
Q

What happens in G2?

A

In G2 the cell continues to grow and energy stores (ATP) are increased

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16
Q

Why in G2 are energy stores increased?

A

Mitochondria increase the energy stores

Energy is needed by cell’s cytoskeleton to transport chromosomes

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17
Q

During G2 what form is DNA in ?

A

During G2 the chromosomes coil back into chromosomes

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18
Q

What happens during the M phase?

A

Cell growth stops
Nuclear division mitosis
Cytokinesis

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19
Q

What does each chromosome pair contain?

A

1 paternal chromosome

1 maternal chromosome

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20
Q

What are homologous chromosomes ?

A

Matching chromosomes
that are the same length/size,
have the same genes/bonding pattern which occurs at the same position loci are known as homologous chromosomes

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21
Q

What is the definition of an allele?

A

An allele is different forms of the same gene

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22
Q

When a cell is not dividing why can you not see any of the chromosomes?

A

When a cell is not dividing you cannot see any of the chromosomes. This is because the DNA is ‘unwound’ chromatin and spread out in the nucleus.

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23
Q

What is the name of the protein molecules in which DNA is wrapped around?

A

The DNA is wrapped around protein molecules called HISTONES

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24
Q

Why happens during the S phase?

What happens just before a cell begins to divide to produce 2 new daughter cells?

A
  • the DNA of each chromosome replicates (DNA REPLICATION)
  • Chromatin must be coiled up (supercoiled) to form visible chromosome
    EACH CHROMOSOME IS SHORT AND STURDY ENOUGH TO BE AROUND EASIER
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25
Q

Does every cell in the body contain exactly the same DNA?

A

Yes

Every cell in the body contain exactly the same DNA

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26
Q

What is peculiar about using the term homologous pair?

A

They’re still referred to as homologous pair although there are 4 chromosomes

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27
Q

What happens when a single chromosome is replicated?

A

When a single chromosome is replicated it forms 2 copies of itself
These 2 copies are called SISTER CHROMATIDS

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28
Q

Describe sister chromatids?

A

Each sister chromatid is an exact copy of the original(single chromosome) and they remain held together at a point called the centromere

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29
Q

What is the centromere ?

A

The centromere is a region of DNA typically found near the middle of a chromosome
Centromeres are involved in linking 2 identical sister chromatids together

30
Q

What is a pair of homologous chromosomes made up of?

A

A pair of homologous chromosome is made up of sister chromatid pairs

31
Q

Can condensed chromosomes perform their normal functions?

A

Condensed chromosomes can be moved around easier
BUT CANNOT perform their normal functions in the cell
So they spend as little time as possible coiled up

32
Q

What happens as chromosomes are being replicated ?

A

Proof-reading enzymes move along the DNA strands and check that the copying has been done properly.

33
Q

Why is it so important that the genetic information is copied and CHECKED?

A

If there is a mutation faulty DNA would be produced
Resulting in daughter cells not having the identical information
Therefore the daughter cells would not function

34
Q

Once a cell has gone through interphase what is the next phase of the cell cycle that it is ready for?

A

Once the cell has done through interphase it is then ready for the next stage of the cell cycle
This next stage is called mitosis

35
Q

What happens in the M-phase?

A

CELL DIVISION

36
Q

What do all eukaryotic multicellular organisms each develop from?

A

All eukaryotic multicellular organisms each develop from a single original cell

37
Q

What is the single original cell from which all eukaryotic multicellular organisms develop from also known as?

A

Fertilised egg

Zygote

38
Q

What does repeated divisons of the zygote by a process of cell division called mitosis give rise to?

A

Repeated division of the zygote (by mitosis) gives rise to all the cells that make up a multicellular organisms

39
Q

What percentage of the correct amount of chromosomes does a haploid cell contain?

A

50% the number of chromosomes

40
Q

What percentage of the correct number of chromosomes does the diploid cell contain?

A

100%

41
Q

Describe the process in order to produce an early embryo?

A

Gametes (haploid) –> zygote (diploid) zygote divides repeatedly by mitosis –> to initially produce a ball of genetically identical cells (early embryo)

42
Q

What is the function of mitosis?

A

The function of mitosis is to produce new identical daughter cells

43
Q

Describe what the daughter cells’ chromosomes are like?

A

The new identical daughter cells each receive a set of chromosomes identical to those of the original parent cell that gave rise to them

44
Q

Why is mitosis so important?

A
  1. Development - the formation of a multicellular organism from a single fertilised egg (zygote)
  2. Growth of cell - involves an increase in size though the division of cells by mitosis
  3. Replacement (repair) - many cells within a multicellular organism are constant dying and being REPLACED by MITOSIS
45
Q

Where are epithelial cells found?

A

Epithelial cells are found lining the intestine

46
Q

How are epithelial cells lining the intestine continually replaced?

A

Epithelial cells lining the intestine are continually being replaced by mitosis

47
Q

How many days does it take for the whole intestine lining to be replaced due to the fact that the epithelial cells are constantly being replaced?

A

Entire lining is replaced every 5 days

48
Q

Where are dead layers of cells found?

A

There are dead layers of cells at the surface of the skin

49
Q

What is constantly happening to the dead layers of cells at the surface of the skin?

A

The dead layers of cells at the surface of the skin are constantly being lost and are replaced by the mitotic divisions of the CELLS IN THE LAYER BENEATH THEM

50
Q

What other separate factor can mitosis be important in?

A

Mitosis can also be important in ASEXUAL REPRODUCTION

51
Q

What can some organisms do to ensure only one parent is needed?

A

Some organisms (e.g. PARAMECIUM, a singled cell organism) and plants can reproduce asexually so that only 1 parent is needed

52
Q

What are the cons of asexual reproduction?

A
  • no genetic variation
  • therefore small gene pool
  • therefore increased susceptibility to being wiped out
53
Q

Mitosis is a continuous process but for convenience is divided into 4 main stages. Name the 4 main stages:

A 
PLEASE MAKE ANOTHER TWO
Prophase
Metaphase 
Anaphase 
Telophase (cytokinesis)
54
Q

Interphase is the previous stage to mitosis

Summarise what happens in interphase:

A
  • during interphase the DNA of the chromosomes replicate (chromatin)
  • DNA is checked for errors
  • protein synthesis
  • synthesis of organelles
  • ATP production
  • cell growth
55
Q

What organelles only replicate in animal cells and not plant cells?

A

Centrioles only replicate in animal cells

56
Q

What do the chromosomes look like in prophase?

A
  • chromosomes condense (shorten and thicken) becoming visible
  • the chromosomes consist of 2 chromatids joined by a centromere
57
Q

In prophase why do the centrioles move to the poles of the cell?

A

In prophase centrioles move to the poles of the cell and form spindle fibres

58
Q

What happens to nuclear envelope during prophase?

A

The nuclear envelope breaks down

59
Q

Why does the nuclear envelope break down?

A

The nuclear envelope breaks down in order to allow the spindle fibres to attach to the chromosomes
To make it easier to move chromosomes

60
Q

During metaphase where do the chromosomes move to?

A

The chromosomes align at the equator

61
Q

Where do the spindle fibres then attach to during metaphase?

A

Spindle fibres attach to centromere

62
Q

What happens to the centromere at anaphase?

A

The centromere splits
Causing the chromatids to separate
The spindle fibres then contract pulling the chromatids to the opposite poles of the cell

63
Q

Describe what is meant by the phrase the centromere leads?

A

Because after the centromere splits during anaphase the chromatids are pulled to the opposite poles of cell - with their centromeres leading first

64
Q

Where are the chromatids positioned in telophase?

A

The chromatids reach the opposite poles on the spindle

65
Q

What do the chromatids then do?

A

They uncoil and de-condense

66
Q

In telophase do the spindle fibres remain intact?

A

No, the spindle fibres begin to disintegrate

67
Q

What then forms around each group of chromosomes?

A

A NUCLEAR ENVELOPE REFORMS around each group of chromosomes

68
Q

What happens to the cytoplasm during cytokinesis?

A

During cytokinesis the cytoplasm divides and now there are two daughter cells that are genetically identical to the original cell and to each other

69
Q

What happens during cytokinesis to the centrioles?

A

The centrioles are replicated

70
Q

Each of the cells created in telophase are diploid cells - what does this mean?

A

Each cell is a diploid cell and contains 2 complete sets (2n) of chromosome

71
Q

How does cell division differ in plants?

A
  • no centrioles
  • cell plate/wall forms between new cells
  • cell division only occurs in MERISTEM PLANTS

Biology A Level (36 decks)

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