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Week10a Flashcards

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AP® Biology flashcards Biology 101 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
Q

(Mitosis)

  1. Anaphase
A
  • 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
Q

(Mitosis)

  1. Telophase
A
  • 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
Q
  1. Cytokinesis

after mitosis

A

• 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
Q

(Prophase)

  1. Chromosomal condensation:
A
  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
Q

(Prophase)

  1. Centrosomes move towards the opposite poles of the cell
A
  1. 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
Q

(Prophase)

  1. Mitotic spindle formation:
A
  1. 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
Q

(Prophase)

3 types of mitotic spindle microtubules :

A

(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
Q

The mitotic spindle:

A
  • 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
Q

(Prophase)

  1. Nuclear envelope and organelle degradation:
A
  1. 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
Q

How do prokaryotes reproduce?

A

• 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
Q

In binary fission:

A
  • The bacterial chromosome replicates

– The two daughter chromosomes actively move apart

36
Q

• Cell division of unicellular eukaryotes:

  • Certain protists
A
  • 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
Q

• Cell cycle stages:

A

➢ 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
Q

Mitosis:

A

: division of nucleus (Prophase, prometaphase,

metaphase, anaphase, telophase)

39
Q

Cytokinesis:

A

division of cytoplasm

Biology (5 decks)

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