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Human Body > 2.1 - Mitosis and Cell Cycle > Flashcards

2.1 - Mitosis and Cell Cycle Flashcards

1
Q

What is typically the goal of cell division?

A

The goal of cell division typically is to equally partition two more-or-less identical copies of genetic material between two daughter cells

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2
Q

Who has an easier time with cell division: Eukaryotes or Prokaryotes?

A

Prokaryotes are comparatively simple, with only one chromosome, so have a relatively easy time sorting daughter chromosomes to daughter cells

Eukaryotes, with their longer DNA and multiple chromosomes, don’t have it nearly so easy

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3
Q

What are chromosomes?

A
  • Chromosomes are tightly packaged DNA
  • They are found only during cell division
  • DNA is not being used for macromolecule synthesis (creation of polymers)
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4
Q

What is chromatin?

A
  • Chromatin is unwound DNA
  • It is found throughout interphase
  • DNA is being used for macromolecule synthesis (creation of polymers)
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5
Q

How is DNA organized?

A

DNA is organized in chromosomes
- Double helix DNA molecule wrapped around histone proteins like thread on spools
- DNA-protein complex = chromatin organized into long thin fiber condensed further during mitosis

Chromatin = long strand of spaghetti (gets squished even smaller during mitosis)

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6
Q

What is a chromatid?

A

Each of the two threadlike strands into which a chromosome divides during cell division. Each contains a double helix of DNA.

Chromosome contains two sister chromatids (lines) that look like this: II

The two sister chromatids are held together by a centromere, making the chromosome look like an X

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7
Q

What is a telomere?

A

A telomere is a compound structure at the end of a chromosome (the tip)

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8
Q

What is a centromere?

A

Centromeres are small round segment that holds two chromatids together.

It is also the region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division.

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9
Q

What is a centrosome?

A

The centrosome is the centre of the microtubule production in a cell. It consists of 2 centrioles.

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10
Q

What is a centriole?

A

A centriole consists of microtubules, and a pair of centrioles makes up a centrosome.

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11
Q

What is a kinetochore?

A

A kinetochore is a protein structure in eukaryotes which assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis.

  • Protein structure near centromere/middle of chromosome where microtubules attach
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12
Q

What is a nucleus?

A
  • Control center of the cell
  • Holds the cell’s genetic material (DNA)
  • Regulates cell activities
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13
Q

What are nucleoli?

A
  • Found inside the nucleus
  • Involved in making components for protein production (ribosomes)
  • Not a separate membrane-bound structure
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14
Q

What are the 4 phases of the cell cycle (in mitosis)?

A

G1, S, G2, mitosis

  • Note: G1, S, and G2 are grouped together as ‘interphase’
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15
Q

What occurs during interphase (general description)?

A

During G1, S, and G2 cell grows and continues to make proteins and organelles

Only replicates DNA during S phase

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16
Q

What are the 2 different kinds of cell life cycle?

A
  • Cell grows/matures to divide again
  • Cell grows/mature to never divide again
17
Q

What kinds of cells divide multiple times?

A
  • Epithelial cells
  • Blood cells
  • Stem cells
18
Q

What kinds of cells divide only once?

A
  • Brain/nerve cells
  • Muscle cells
19
Q

What occurs during G1 phase?

A

Beginning of a cell’s life:
- Follows Cytokinesis
- Cell begins growing to full size
- Transcription and Translation occur
- DNA only in single strands now

20
Q

What occurs during S phase?

A

DNA replicates itself (makes 2 double stranded DNA molecules):
- No more RNA will be made BUT leftover RNA (translation) can still be used for repairs etc.
- Centrosomes replicate
- Cells which do not go through this phase – can’t divide. (Eg. brain cells, some nervous tissue)*

  • Research with this might help cancer
21
Q

What occurs during G2 phase?

A

Nucleus is well defined and still has the membrane
- Centrosomes present
- Chromosomes (DNA) has duplicated but is still a mess of strands
- New RNA transcribed to make proteins necessary for division – spindle fibers
- Leftover RNA (S phase) is used now for repairs

Cells are ready for mitosis

22
Q

By the end of G2 phase, what qualities does the cell have?

A
  • Nucleus is defined
  • Nucleoli are present
  • Replicated Centrosomes
  • DNA is duplicated
  • DNA is still chromatin
23
Q

Define mitosis

A

Mitosis is unicellular reproduction (making 2 cells out of 1)

24
Q

What is mitosis used for?

A
  • Used for repair, growth, and development from a fertilized egg
  • Used to produce somatic cells (not sexual cells - gametes)
25
Q

What is the end result of mitosis?

A

Mitosis yields 2 identical daughter cells (produced asexually)

26
Q

How is mitosis affected by genetic variation?

A

Genetic variation is comparatively slow in mitosis (MUCH greater in meiosis)

27
Q

What are the 4 stages of mitosis?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
28
Q

What occurs during prophase (mitosis)?

A
  • Chromatin fibers condense, becoming more coiled
  • Chromosomes are seen as two identical sister chromatids
  • Nucleoli vanish, and the nuclear membrane starts breaking down
  • A mitotic spindle forms from centrioles
  • Centrosomes move apart to poles
  • No more RNA is transcribed
  • The nucleus is still visible, and chromosomes are condensing, becoming thicker and visible
29
Q

By the end of prophase, what has occured?

A
  • Chromosomes condense
  • Nucleoli vanish
  • Mitotic spindle forms
  • Centrosomes move apart
30
Q

What occurs during prometaphase?

A

In the transition from prophase to metaphase:

  • Nuclear envelope breaks apart
  • Microtubules enter the nucleus and engage with chromosomes
  • Kinetochores (handles for mitotic spindle) form at centromeres
31
Q

What occurs during metaphase?

A
  • Spindle fibers connect with chromosomes
  • Centrioles are now on opposite sides
  • Fibers grab onto kinetochore
  • Chromosomes form a line in the middle of the cell (called metaphase plate)
  • The nucleus breaks down, and chromosomes line up in the middle
32
Q

By the end of metaphase, what has occured?

A
  • Centrosomes are at opposite poles
  • Metaphase plate is formed
  • Chromosomes line up on the plate
  • Mitotic spindle is in action
  • Brief, static phase
33
Q

What occurs during anaphase?

A
  • Sister chromatids split, moving to opposite poles of cell
  • By the end, each pole has a complete set of chromosomes.
  • Spindle fibers move chromosomes apart (chromosomes split and go to opposite sides).
34
Q

By the end of anaphase, what has occured?

A
  • Starts with “sister” separation
  • Chromatids become chromosomes
  • “Sisters” go to opposite ends
  • All movement led by centromeres
  • Poles separate even more
35
Q

What occurs during telophase?

A
  • Unconnected microtubules move even farther
  • New nuclei start to form
  • Protective membrane around nuclei begins to reappear
  • Chromatin is now less tightly wound
36
Q

By the end of telophase, what has occured?

A
  • “Sisters” are at opposite ends
  • Protective layer around nuclei is reforming
  • Chromosomes are relaxing
  • Cytokinesis (cell division) is already happening
37
Q

What is cytokinesis?

A

Cell division ends with cytokinesis in telophase. This is when the cell actually splits into two identical daughter cells.

38
Q

How is cytokinesis different in animals and plants?

A
  • Animals have a tightening middle part (cleavage furrow) like squeezing a water balloon
  • Plants use a cell plate (a line forms within the cell wall) to divide the cell
39
Q

What is the role of microtubules in mitosis?

A

Microtubules create spindle fibers that pull and arrange chromosomes, ensuring they separate correctly and go to the right places in daughter cells.

Human Body (22 decks)

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