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A-Level Biology > Cell Structure - All cells arise from other cells > Flashcards

Cell Structure - All cells arise from other cells Flashcards

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1
Q

What is a chromosome

A

A DNA molecule folded into a condensed form, wrapped around histone proteins in eukaryotes

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2
Q

Define the term homologous chromosome

A

Have the same genes but may have different alleles

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3
Q

Define the term diploid

A

Cells with homologous pairs of chromosomes and is represented as 2n

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4
Q

Define the term haploid

A

Cells with one copy of each homologous pair of chromosomes and is represented by n

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5
Q

What are the stages of the cell cycle

A
  1. Interphase
  2. Prophase
  3. Metaphase
  4. Anaphase
  5. Telophase
  6. Cytokinesis
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6
Q

What happens during interphase

A
  • New proteins are synthesised
  • DNA replicates
  • New organelles are made
  • Individual chromosomes are not visible at this stage
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7
Q

Why must DNA replication occur before cell division

A

SO that 2 genetically identical daughter cells are produced

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8
Q

What happens in metaphase

A
  1. Spindle fibres attach to the centromere of each chromosome
  2. The chromosomes are moved to the equator of the cell by the spindle fibres
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9
Q

What happens in prophase

A
  1. The nuclear membrane breaks down
  2. Centrioles move to the poles of the cell and make spindle fibres
  3. The chromosomes condense and become visible. Each chromosome is made up of 2 sister chromatids joined at the centromere
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10
Q

Why is mitosis important to organisms

A
  1. It allows the organism to grow
  2. Allows organisms to replace cells in order to repair tissues
  3. Results in genetically identical cells
  4. Asexual reproduction in some organisms
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11
Q

What happens in telophase

A
  1. Chromosomes have reached the poles and the spindle fibres break down
  2. A new nuclear membrane forms around each group of chromosomes
  3. The chromosomes un-condence and begin to form chromatin again
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12
Q

What happens in anaphase

A
  1. The centromere divides
  2. The spindle fibres contract, sister chromatids are pulled apart to the opposite poles of the cell
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13
Q

What happens in cytokinesis

A

The cytoplasm divides, producing 2 genetically identical daughter cells

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14
Q

How do you calculate mitotic index?

A

Mitotic index = Number of cells undergoing mitosis / Total number of cells

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15
Q

How to calculate the length of a certain stage of mitosis

A

Length of … = (Number of cells in certain stage / Total number of cells) x time of 1 cell cycle

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16
Q

What is cell division like in a cancer cell

A
  • Divide uncontrollably
  • Have a shorter cell cycle
  • Divide more often
17
Q

How do cancer treatmants prevent tumour formation

A

Drugs may stop
- DNA replication (disrupts interphase)
- Spindle formation / spindle contraction (prevents metaphase / anaphase)
- Cytokinesis

18
Q

What are the problems with cancer treatments

A

These treatments do not always distinguish tumour cells from healthy cells from healthy cells, so they also kill some normal body cells that are dividing, causing side effects

19
Q

How do prokaryotes divide

A

Binary Fission

20
Q

What are the stages for prokaryotic replication

A
  1. The circular DNA and the plasmids replicate
  2. The copies of circular DNA move to separate poles of the cell
  3. The cytoplasm divides to produce 2 daughter cells
  4. Each cell contains a single copy of the circular DNA but a variable number of plasmids
21
Q

Why do cancer treatments kill more cancer cells than healthy cells

A

Tumour cells divide more frequently than normal body cells

22
Q

Why do viruses only infect specific host cells

A

Since they are unloving and acellular they do not undergo cell division

23
Q

Why are viruses so difficult to treat

A

They replicate inside the cells where the drug is unable to bind to them

24
Q

What are the stages of viral replication

A
  1. The virus attachment protein binds to a specific complementary receptor protein on a specific host cell
  2. The viral DNA / RNA is injected into the hist cell
  3. The host cell uses the viral DNA / RNA and its own ribosomes and enzymes to synthesise viral proteins
  4. The viral particles are formed and released from the host cell

A-Level Biology (19 decks)

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