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Biology (Year 1) > 3.2.2 All cells arise from other cells > Flashcards

3.2.2 All cells arise from other cells Flashcards

1
Q

What are the three stages of the cell cycle ?

A
  • Interphase (G1, S, G2)
  • Nuclear division (mitosis)
  • Cell division (Cytokinesis)
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2
Q

What is interphase and what are the three main stages?

A

organelles double and DNA replicates but the cell continues to carry out normal functions
Stages = G1, S, G2

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3
Q

What occurs during the G1 stage of interphase ?

A
  • Cells make RNA, enzymes and proteins for growth
  • A signal is received telling the cell to divide
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4
Q

What occurs during the synthesis stage of interphase ?

A

*** DNA in the nucleus replicates **(each chromosome has two identical sister chromatids)

relatively short stage

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5
Q

What occurs during the G2 stage of interphase ?

A
  • **cell continues to grow and the new DNA that has been synthesises is checked **
  • other substances needed for division are also made (eg proteins)
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6
Q

Define mitosis

A

a eukaryotic cell divides to produce two genetically identical daughter cells
- each with identical copies of the DNA produced by the parent cell

Two divisions - Diploid daughter cells (complete set of chromosomes)

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7
Q

Give the three main uses of mitosis

A
  1. growth of multicellular organisms
  2. repair and replacement of cells -produce new cells with an identical structure and function
    3.** asexual reproduction **- genetically identical diploid daughter cells
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8
Q

Describe what happens during prophase

A
  • chromosomes condense and become visible (when stained)
  • Nuclear envelope breaks down
  • Nucleolus breaks down
  • **centrioles move to opposite poles **and spindle fibres emerge from the centrioles- form a spindle aparatus

spindle fibres = protein microtubules

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9
Q

Describe the composition of the chromosomes in prophase

A

two identical sister chromatids joined at the centromere
(the chromosomes are replicated during the synthesis stage of interphase)

Each chromatid contains one DNA molecule
Centromere - site of attachment for spindle fibres

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10
Q

Describe what happens during metaphase

A
  • centrioles reach the opposite poles
  • **Spindle fibres reach the chromosomes **and attach to centromeres
  • chromosomes are pulled along the spindle apparatus and** line up along the cell equator**
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11
Q

Describe what happens during anaphase

A
  • spindle fibres retract, which puts tension on the centromere
  • centromere divides in two - separates the sister chromatids
  • Chromatids are pulled to opposite poles
  • They are now called **chromosomes **again

This stage requires energy from the mitochondria

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12
Q

Describe what happens during telophase

A
  • chromosomes reach the opposite poles
  • they begin to decondense/uncoil (no longer visible)
  • spindle fibres break down
  • nuclear envelope reforms - two new nuclei

Each chromatid now contains one DNA molecule which will replicate itself during interphase before the next division

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13
Q

Describe what happens during cytokinesis

A

the **cytoplasm divides **forming two genetically identical daughter cells

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14
Q

How does cytokinesis vary in animal and plant cells ?

A

Animal
- cleavage furrow forms to separate the daughter cells
Plant
- cell plate forms at the equator, stimulating the production of new cell walls

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15
Q

State the difference between diploid and haploid cells

A

Diploid
- Two sets of chromosomes (46 in humans - 23 pairs)
- Two diploid cells produced in mitosis

Haploid
- Single set of chromosomes (23 total)
- Four haploid cells produced during two divisions in meiosis

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16
Q

What is the function of spindle fibres ?

A

separation of sister chromatids and movement of chromosomes during mitosis

17
Q

Define mutation

A

a change in the base sequence of an organisms DNA
- can cause uncontrolled cell division and tumour formation

18
Q

Define benign vs malignant

A

Benign - do not spread from the original site
Malignant - invade surrounding tissue

19
Q

What are the four main stages of cancer development ?

A

1.** Oncogenes** (mutated genes that cause cancer) arise due to carcinogens
2. cancer cells** divide uncontrollably by mitosis**
3. malignant tumour cells can break off and** travel through the blood/lymphatic system to form secondary growths**
4. invasion of other tissues interupts normal functioning

20
Q

Define metastasis

A

spreading of cancer cells to other parts of the body, forming secondary growths

21
Q

Why does cancer treatment often involve blocking some parts of the cell cycle ?

A

disrupts cell division, which inhibits cancer cell growth

22
Q

Which two parts of the cell cycle are typically targeted during chemotherapy ?

A
  • G1 phase - prevents synthesis of enzymes for DNA replication
  • Metaphase (interferes with spindle formation) - prevents chromatids lining up, so they cannot divide
23
Q

Wht are the issues with targeting the cell cycle during cancer treatment ?

A
  • also disrupts the cell cycle of normal cells
  • so can result in sickness and hair loss

However cancer cells divide more rapidly so are damaged to a greater extent

24
Q

Define binary fission

A

a form of asexual reproduction in which the organism divides into two genetically identical copies

occurs in prokaryotic cells

25
Q

Describe the three main stages of binary fission

A
  1. **circular **DNA and plasmids replicate (DNA replicates once, plasmids many times)
  2. DNA loops move to opposite poles
  3. **cytoplasm divides into two **and a new cell wall - forms daughter cells

Each daughter cell has ONE DNA loop and a variable number of plasmids

26
Q

Describe the three main stages of viral replication

Viruses are non-living so cannot undergo cell division themselves

A
  1. ATTACHMENT - **attachment proteins **(on the virus) bind to the complementary receptor proteins on the host cell
  2. ENTRY - viral DNA is injected
  3. REPLICATION - viral DNA provides the instructions for the host cell to produce nucleic acids, enzymes and structural proteins which form the new viruses**
  4. Host cell bursts - releasing the new viruses
27
Q

When are chromosomes visible?

A

prophase, metaphase, anaphase and telophase
(in interphase they are decondensed and so not visible)

Biology (Year 1) (15 decks)

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