All cells arise from other cells (3) Flashcards

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1
Q

What is the cell cycle?

A

cycle of division with intermediate growth periods

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2
Q

What are the 3 stages of the cell cycle?

A

1) interphase
2) mitosis/meiosis (nuclear division)
3) cytokinesis (cytoplasmic division)

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3
Q

What are the 3 stages of the interphase?

A

G1
S
G2

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4
Q

What happens in the G1 stage?

A

cell synthesises proteins for replication, e.g. tubulin for spindle fibres, and cell size doubles

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5
Q

What happens in the S stage?

A

DNA replicates so chromosomes consist of 2 sister chromatids joined at a centromere

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6
Q

What happens in the G2 stage?

A

organelles divide

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7
Q

Why does the cell cycle not occur in some cells?

A

because after differentiation, some types of cell in multicellular organisms (e.g. neurons) no longer have the ability to divide

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8
Q

What is the result of mitosis?

A

produces 2 genetically identical daughter cells

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9
Q

What is the purpose of mitosis?

A

(produces 2 genetically identical daughter cells) for:
- growth
- cell replacement/tissue repair
- asexual reproduction

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10
Q

What are the 4 stages of mitosis?

A

1) prophase
2) metaphase
3) anaphase
4) telophase

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11
Q

What are the 3 steps of the prophase?

A

1) chromosomes condense, becoming visible (can see X shape of 2 sister chromatids joint at the centromere)
2) centrioles move to opposite poles of cell and mitotic spindle fibres form
3) nuclear envelope and nucleolus break down so chromosomes become free in cytoplasm

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12
Q

What happens during the metaphase?

A

sister chromatids line up at cell equator and are attached to mitotic spindle fibre by their centromeres

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13
Q

What are the 2 steps of the telophase stage?

A

1) chromosomes decondense, becoming invisible again
2) new nuclear envelopes form around each set of chromosomes so there are 2 new nuclei, each with 1 copy of each chromosome

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14
Q

What are the names and colours of 2 dyes that bind to chromosomes?

A

toluidine blue (blue)
acetic orcein (purple-red)

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15
Q

What are the 3 steps of the anaphase stage?

A

1) spindle fibres contract so centromeres divide
2) sister chromatids separate into 2 distinct chromosomes and are pulled to opposite poles of cell
3) spindle fibres break down

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16
Q

What does the anaphase require?

A

energy from ATP hydrolysis

17
Q

Which stage of mitosis requires energy from ATP hydrolysis?

A

anaphase

18
Q

What does the anaphase look like in a diagram?

A

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19
Q

What are the 3 steps of the procedure for the root tip squash experiment?

A

1) prepare temporary mount of root tissue
2) focus an optical microscope on the slide and count total number of cells in the field view and number of cells in a mitosis stage
3) calculate the mitotic index

20
Q

What is the mitotic index?

A

proportion of cells undergoing mitosis

21
Q

What are the 4 steps on how to prepare a root tip mount?

A

1) place root in hydrochloric acid to halt cell division and hydrolyse middle lamella
2) strain root tip with a dye that binds to chromosome
3) macerate tissue in water using mounted needle
4) use mounted needle at 45 degrees to press down coverslip and obtain a single layer of cells and avoid trapping air bubbles

22
Q

Why is only the root tip use when calculating a mitotic index?

A
  • meristematic cells at root tip are actively undergoing mitosis
  • cells further from root tip are elongating rather than dividing
23
Q

What are tumour suppressor genes?

A

genes that code for proteins to trigger apoptosis/slow cell cycle

24
Q

What is apoptosis?

A

programmed death of damaged cells

25
Q

What are proto-oncogenes?

A

genes that code for proteins to stimulate cell cycle to progress from 1 stage to the next

26
Q

How do cancer treatments control rate of division?

A

disrupt cell cycle:
- prevent DNA replication
- disrupt spindle formation which inhibits metaphase and anaphase

27
Q

What is one issue with cancer treatments?

A

can also damage healthy cells

28
Q

How can mutations to tumour suppressor genes cause cancer?

A
  • no production of a protein needed to slow the cell cycle
  • disruption to cell cycle causing uncontrolled cell division which leads to a tumour
29
Q

How can mutations to proto-oncogenes cause cancer?

A
  • form permanently-activated oncogenes
  • disruption to cell cycle causing uncontrolled cell division which leads to a tumour
30
Q

What are the 4 steps on how prokaryotic cells replicate via binary fission?

A

1) DNA loop replicates, both copies stay attached to cell membrane, plasmids replicate in cytoplasm
2) cell elongates, separating the 2 DNA loops
3) cell membrane contracts and septum forms
4) cell splits into 2 identical progeny cells, each with 1 copy of the DNA loop but a variable number of plasmids

31
Q

What are the 4 steps on how a virus replicates?

A

1) attachment proteins attach to receptors on host cell membrane
2) enveloped viruses fuse with cell membrane or move in via endocytosis and either release DNA/RNA into the cytoplasm or inject the DNA/RNA
3) host cell uses viral genetic information to synthesis new viral proteins/nucleic acid
4) components of new viral particle assemble

32
Q

What happens to new viral particles which leave host cell?

A

they either bud off and use cell membrane to form envelope or cause lysis of host cell

33
Q

Why is it difficult to develop effective treatments against viruses?

A

they replicate inside living cells so it’s difficult to kill them without killing host cell

34
Q

What is one issue with viruses?

A

it’s difficult to develop effective treatment against them