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Week10a Flashcards

1
Q

Cell division

A

-reproduction of cells

• The continuity of life is based upon cell division

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2
Q

Unicellular organisms:

Multicellular organisms

A

➢ Unicellular organisms: Reproduction by cell division (e.g.
binary fission)

➢ Multicellular organisms depend on cell division for:
– Growth
– Development from a fertilized cell
– Repair of damaged tissues

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3
Q

Mitosis:

Meiosis:

A

– Mitosis: production of somatic cells (diploid cells)

– Meiosis: production of gametes (haploid cells)

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4
Q

Difference between

Mitosis:
and
Meiosis:

A

• Mitosis: conserves the chromosome number of the cells

=> production of 2 genetically identical cells that are also
genetically identical to the parental cell

• Meiosis: reduces the chromosome number in half

=> production of gametes in the gonads

=> Fertilization: A male and female gamete (haploid cells) fuse
producing a zygote with a complete set of chromosomes (diploid)

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5
Q

Cell cycle

define?
Stages?

A

• The functional process that a cell goes through until it is
divided in 2 identical daughter cells

• Phases (stages) of the cell cycle:

  • G1 (gap 1): preparation of the cell for DNA replication
  • S phase (synthesis): DNA replication
  • G2 (gap 2): preparation for cell division
  • M phase (mitotic phase): cell division (mitosis)
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6
Q

Two phases of the cell cycle

A

– Interphase: G1, S and G2 phases

– Mitotic phase: Mitosis and Cytokinesis

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7
Q

Mitosis includes what?

A 
Prophase,
Prometaphase,
Metaphase,
Anaphase,
Telophase
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8
Q

G0 phase:

found on top of G1 in pic btw

A
  • Resting phase: non-dividing cells are resting at this
    phase

• Differentiated cells enter from G0 to G1 after the action of growth factors

• Cells exit G1 and enter G0
(G1 → G0) in order to
differentiate

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9
Q

Cell cycle control:

signal types?

A

Εxtracellular signals (e.g. presence of growth factors)

  • Intracellular signals (e.g. cell size)
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10
Q

Cell types according to their cell division potential

A
  • Post-mitotic cells:
  • Cells that divide upon appropriate stimulation (signal):
  • Cells with high mitotic activity:
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11
Q

Post-mitotic cells:
what is it?
example?

A

: terminally differentiated cells which have lost their ability to replicate => permanently arrested at G0 phase

  • Example: neural cells, cardiac muscle cells, red blood cells
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12
Q

Cells that divide upon appropriate stimulation (signal):

examples?

A
  • Example: most of the cells in our body only divide upon
    stimulation by growth factors or other signal
  • e.g. lymphocytes upon antigenic presentation
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13
Q

Cells with high mitotic activity:

A

e.g. germ cells, stem

cells, epithelial cells

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14
Q

What is Interphase
3 facts?
Stages?

A
  • The period between cell divisions
  • The larger phase of the cell cycle
  • The cell prepares for cell division

• The cell decides whether or not it will proceed with cell
division

• Includes the 3 first phases of the cell cycle:
- G1, S, G2 phases

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15
Q

What do cells have to do Before cell division (during interphase):

A
  1. Cell components have to replicate (organelles,
    membranes, proteins)
  2. Chromosomes need to replicate

➢ Genetic material needs to replicate in order for daughter
cells to have the same genome as the parental cell
➢ This ensures their survival

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16
Q

the 3 sub- phases of INTERPHASE:

A

• G1 phase: preparation for DNA replication
- Protein synthesis, organelle production

• S phase: DNA synthesis (replication)

• G2 phase: preparation for cell division (mitosis)
- Protein synthesis, organelle production

17
Q

Eukaryotic chromosomes:

A

– Consist of chromatin, a complex of DNA and proteins
(histones)

– Each chromosome carries a few hundred to a few
thousand genes

18
Q

Somatic cells:

Gametes (reproductive cells):

A

Somatic cells: diploid cells (2n, n =23 chromosomes)

  • have 2 sets of 23 chromosomes = 46 total => 23 chromosome pairs
  • Each homologous chromosome pair has 1 paternal
    and 1 maternal chromosome

Gametes (reproductive cells): haploid cells (n, n =23
chromosomes)
– have one set of chromosomes = 23 total
– Have only 1 chromosome (either paternal or maternal)
from each homologous chromosome pair

19
Q

Somatic cells:

A

Somatic cells: diploid cells (2n, n =23 chromosomes)

  • have 2 sets of 23 chromosomes = 46 total => 23 chromosome pairs
  • Each homologous chromosome pair has 1 paternal
    and 1 maternal chromosome
20
Q

Gametes (reproductive cells):

A

Gametes (reproductive cells): haploid cells (n, n =23
chromosomes)

– have one set of chromosomes = 23 total

– Have only 1 chromosome (either paternal or maternal)
from each homologous chromosome pair

21
Q

Differnces in
-Interphase
and
-Mitosis

A

• Interphase: chromosomes are not condensed

– G1 phase: each chromosome consists of one
chromatid (not replicated yet)

– S phase: DNA is replicated

– G2 phase: Each duplicated chromosome has 2 sister
chromatids

• Mitosis (cell division):

  • the chromosomes condense => can be seen with a light microscope
  • sister chromatids separate => each future daughter
    cell receives one chromatid
22
Q

(Mitosis)

1.Prophase

A
  • The chromatin fibers condense into distinct chromosomes
  • The nucleoli disappear, nuclear membrane degradation begins

• The mitotic spindle (composed of centrosomes and
microtubules) begins to form

23
Q

(Mitosis)

2.Prometaphase

A

• The nuclear envelope fragments

• The microtubules extending from each centrosome can
invade the nuclear area and bind to the chromosomes

• The chromosomes become more condensed

24
Q

(Mitosis)

  1. Metaphase
A

• The centrosomes are now at opposite poles

• The chromosomes are aligned on the metaphase plate
imaginary plane equidistant between the spindle’s two poles

25
(Mitosis) 4. Anaphase
* The sister chromatids of each chromosome move towards opposite poles * By the end of anaphase the two poles of the cell have equivalent collections of chromosomes (chromatids)
26
(Mitosis) 5. Telophase
* Nuclear envelops reform * Nucleoli reappear * Two daughter nuclei form in the cell * Chromosomes decondense • Mitosis (the division of one nucleus into two genetically identical nuclei) is now complete
27
6. Cytokinesis | after mitosis
• Cytokinesis: the cells are completely separated. • The division of the cytoplasm usually begins by late telophase so the two daughter cells appear shortly after the end of mitosis. • In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow.
28
(Prophase) 1. Chromosomal condensation:
1. Chromosomal condensation: - Interphase: the chromosomes are decondensed (loose form of chromatin) => to help replication and transcription - Μitosis: chromosomal condensation => begins at prophase - Prophase: each chromosome consists of 2 sister chromatids (it is duplicated) - Sister chromatids = DNA copies (replicated during S phase) - sister chromatids are joined by centromeres - Centromeres: consist of repetitive DNA sequences
29
(Prophase) 2. Centrosomes move towards the opposite poles of the cell
2. Centrosomes move towards the opposite poles of the cell - Usually found next to the nucleus (cell center) - Centrosome replication: during S phase 2 new centrosomes during mitosis After mitosis: 1 centrosome per cell
30
(Prophase) 3. Mitotic spindle formation:
3. Mitotic spindle formation: - Mitotic spindle begins to form by the polymerisation of microtubules - Microtubule polymerisation starts from the centrosome - Κinetochores: protein structures found at the centromere of each chromosome - 1 kinetochore/chromatid - mitotic spindle microtubules attach to the kinetochores of the chromatids => move chromosomes towards the metaphase plate - Attachment point for motor proteins
31
(Prophase) 3 types of mitotic spindle microtubules :
(a) Αstral microtubules: - radial (star-like) structure around the centrosome - Function: positioning of the spindle in the cell (b) Kinetochore (chromosomal) microtubules: - join the centrosome with the kinetochores (centromeres) of the chromosomes - Function: chromosomal movement (c) Polar microtubules: - start from the centrosome but do not attach to the chromosomes - interact with other polar microtubules projecting from the other pole - Function: maintain the integrity of the spindle
32
The mitotic spindle:
- an apparatus of microtubules that controls chromosome movement during mitosis - arises from the centrosomes or other MTOC - includes spindle microtubules (kinetochore and polar) and astral microtubules • Animal cells: MTOC= centrosome made by two centrioles • Plant cells: have different type of MTOC (lack centrioles)
33
(Prophase) 4. Nuclear envelope and organelle degradation:
4. Nuclear envelope and organelle degradation: - Nuclear lamin phosphorylation (nuclear envelope components) - Lamins: intermediate filaments present in the nuclear lamina Nuclear envelope degradation and packaging into vesicles - Endoplasmic reticulum and Golgi apparatus are also degraded and packaged into vesicles => they will later be separated into the daughter cells
34
How do prokaryotes reproduce?
• Prokaryotes (bacteria) do not have an organized reproductive cell cycle => do not reproduce by mitosis • Prokaryotes reproduce by another type of cell division called binary fission • Binary fission is a very simple cell division process => much faster than eukaryotic cell cycle – bacterial replication time is 1-3 h
35
In binary fission:
- The bacterial chromosome replicates – The two daughter chromosomes actively move apart
36
• Cell division of unicellular eukaryotes: - Certain protists
- Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis carried out by most eukaryotic cells (e.g. multiple fission)
37
• Cell cycle stages:
➢ G1 phase: preparation for DNA replication ➢ S phase: DNA replication ➢ G2 phase: preparation for cell division (mitosis) ➢ M phase: cell division (mitosis) • G0: Non-dividing cells
38
Mitosis:
: division of nucleus (Prophase, prometaphase, | metaphase, anaphase, telophase)
39
Cytokinesis:
division of cytoplasm

Biology (5 decks)

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