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Biology A1 > 8B: Mitosis & Cancer > Flashcards

8B: Mitosis & Cancer Flashcards

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1
Q

The nucleus of all ________ cells contains a set number of ______ depending on the species

A
  1. eukaryotic cells
  2. chromosomes
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2
Q

How many Chromosomes do Humans have?

A
  • 23 homologous pairs
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3
Q

What is the diploid number of chromosomes? (human)

A

46

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4
Q

Explain what happens to Chromosomes prior to cell division:

A
  1. the DNA in the chromosomes replicate (semi-conservative) all the way along its length
  2. each chromosome becomes 2 threads called chromatids held together at the centrometre
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5
Q

How do chromosomes become more clear?

A
  • as cell division begins, the chromosomes shorten and thicken (condense) because the DNA coils up tightly around the histone proteins
  • the chromosomes therefore become clearly visible as separate structures
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6
Q

Chromosome Definition:
Chromatid Definition:
Homologous Chromosomes Definition:

A
  1. long, linear structures consisting of DNA and histone proteins
  2. one of the 2 threads of a chromosome formed after DNA replication, (each chromatid in a chromosome is an exact copy of the other, sister chromatids)
  3. a pair of chromosomes containing the same genes in the same position (loci), each derived originally from a different parent’s gamete at fertilisation (so could have different alleles)
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7
Q

Describe the key features of Mitosis:

A
  • each parent cell divides to form 2 daughter cells
  • each daughter cell contains an exact copy of the DNA of a parent cell (genetically identical)
  • this is due to DNA replication produces 2 chromatids in one chromosome BEFORE MITOSIS
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8
Q

What is the benefit of Mitosis?
How does this affect growth and repair?

A
  • allows asexual reproduction, which produces offspring genetically identical to parent
  • increases the number of cells during growth
  • replaces tissues with a new group of cells during repair
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9
Q

What is the only way variation can occur during mitosis?

A
  • mutation
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10
Q

In Eukaryotic Cell Division the ____ divides first, then the _____ divides to form 2 new daughter cells

A
  1. nuclei (forming two new nuclei)
  2. cytoplasm
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11
Q

What is the stage before Mitosis?
Explain:

A

interphase: cell makes preparations ready for cell division
- DNA has replicated (semi-conservative)
- cell is actively synthesising proteins, with an increase in organelle + ATP production
- chromosomes are visible prior to mitosis

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12
Q

What is the first step of Mitosis?

A
  1. Prophase:
    - nuclear membrane breaks down, + nucleolus disappears
    - leaving the DNA in Chromosomes free in cytoplasm
    - the Chromosomes contract + become shorter (condense due to the coiling of DNA tightly around histones making them visible)
    - Centrioles divide and move to the poles of the cell, with spindle fibres forming across the cell from the centrioles
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13
Q

What is the second step of Mitosis?

A
  1. Metaphase:
    - the chromosomes move/line up at the equator of the cell/spindle
    - chromosomes attach to these spindle fibres at the centromere
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14
Q

What is the function of the Centromere?

A
  • holds the two chromatids together (replicated chromosome)
  • allows the chromosomes to attach to the spindle fibres
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15
Q

What is the third step of Mitosis?

A
  1. Anaphase:
    - spindle fibres contract
    - this causes the centromere which hold together the 2 chromatids break
    - therefore, each chromatid from a chromosome will be pulled to opposite poles of the cell
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16
Q

What is the fourth step of Mitosis?
What marks the end of Mitosis (this sometimes happens during this stage)?

A
  1. Telophase:
    - chromatids still lie at the poles of the cell
    - nuclear membrane/envelope forms around each set of chromosomes (so the cell has 2 nuclei briefly)
    - nucleolus reforms
    - chromosomes unwind and diffuse so become no longer visible
  2. Cytokinesis:
    - division of the cytoplasm begins with pinching along the equator of the cell
    - new cell membrane forms in the middle of the cell to separate the two nuclei into 2 new cells
    - cell membrane of one side of the cell joins with the new membrane to form 2 new daughter cells
    - in plant cells cellulose builds up after to form the cell wall
17
Q

What are the 4 stages of the Cell Cycle?

A

G1: cells prepare for DNA replication
S: DNA replication occurs
G2: relatively short gap before mitosis
M: mitosis occurs

18
Q

Which phases of the Cell Cycle correspond to Interphase?
What happens to the newly produced daughter cells from mitosis?

A

G1, S, G2
enter interphase, cycle continues

19
Q

The duration of _________ in the cell cycle gives us information on the ____ _____ _______ ______

A
  1. interphase
  2. rate of cell division (shorter interphase divides more often e.g cancer cells + hair cells, whereas other cells can remain in interphase for months e.g liver)
20
Q

What is the G0 stage of the Cell Cycle?

A
  • G0 is for cells which do not retain the ability to divide e.g muscle + neuron cells, these lie outside the cell cycle
21
Q

mitotic index formula

A

mitotic index = number of cells undergoing mitosis/ total number of cells
(note- telophase/cytokinesis can be put together as sometimes cytokinesis occurs before telophase has finished)

22
Q

How do Prokaryotic Cells divide?

A

Binary Fission:
- replication of the circular DNA, including plasmids
- cell membrane begins to grow in between two main DNA loops and begins to pinch inwards, dividing the cytoplasm in two
- new cell wall forms between two DNA loops, forming two daughter cells each with a copy of main circular DNA and a variable number of copies of plasmids

23
Q

How do Viruses replicate?

A
  • the attach to the host cell’s receptors using their attachment proteins on their surface
  • they then inject their nucleic acids into the host cell
  • this is used to produce new viral components ( e.g capsid , proteins) that are assembled into new viruses
24
Q

What is Cancer?

A
  • mutations of genes that control cell division, causing rapid, uncontrolled division of cells
  • this results to the formation of a mass of abnormal cells (tumour)
  • cancerous tumour cells do not respond to signals from nerves and hormones as normal healthy cells would, and do not undergo programmed cell death (apoptosis), which would usually happen when irreparable damage is detected
25
Q

Give an example of how Cancer may develop:

A
  1. protein called p53 normally stops the cell cycle, to prevent faulty cells from dividing and forming faulty daughter cells
  2. p53 gene codes for production of p53 protein
  3. mutation of the p53 gene means no p53 protein is made (or is non-functional)
  4. cell with damaged DNA completes Cell Cycle + divides
  5. uncontrolled cell division produces cancer
26
Q

Describe 2 ways cancer can be treated:

A
  • preventing DNA from replicating
  • preventing the formation of spindle fibres, or disrupting another stage of mitosis

Biology A1 (15 decks)

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