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Intro to Molecular Biology & Genetics > Intro Molecular Biology REVISION (pt1) > Flashcards

Intro Molecular Biology REVISION (pt1) Flashcards

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1
Q

Stages of the cell cycle in eukaryotic cells

5

A
  • G1
  • S
  • G2
  • Mitosis (+cytokinesis)
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2
Q

what happens in the interphase ?

A
  • G1
  • S
  • G2
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3
Q

what happens is G1 ?

A
  • Growth phase
  • Increase metabolic/biosynthetic activity
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3
Q

what happens is G1 ?

A
  • Growth phase
  • Increase metabolic/biosynthetic activity
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4
Q

what 3 options doe the G1 phase have ?

A
  1. To continue cell cycle and enter S phase
  2. Stop cell cycle and enter G0 (resting phase) for undergoing differentiation
  3. Become arrested in G1 phase and entre the G0 phase or re-entre cell cycle
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5
Q

what happens is the S phase ?

A

DNA synthesis commences

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6
Q

what happens in the G2 phase ?

A
  • Occurs after DNA replication and is a period of protein synthesis and rapid cell growth to prepare the cell for mitosis
  • Before proceeding to mitotic phase, cells must be checked at the G2 checkpoint for any DNA damage within the chromososmes
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7
Q

what happens in the Mitosis ?

A

Consists of nuclear division (karyokinesis)

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8
Q

what are the stages of Mitosis

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
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9
Q

what happens in the prophase ?

A
  • cell prepares to divide by tightly condensing its chromosomes
  • initialisation of mitotic spindle formation
  • Gene transcription ceases until late anaphase to early G1
  • Centrosomes coordinate cell’s microtubules
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10
Q

what happens in the prometaphase ?

A
  • Phosphorylation of nuclear lamins = nuclear envelope disintegrates into small membrane vesicles
  • microtubules invade the nuclear space
  • late stage = kinetochore microtubules attach to chromosomal kinetochores
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11
Q

what happens in the metaphase ?

A
  • 2 centrosomes begin to pull chromosomes towards opposite poles of the cell
  • checkpoint to guarantee that kinetochores have properly attached to the mitotic spindle + alignment of chromosomes along metaphase plate
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12
Q

what happens in anaphase?

A
  • cohesins bind sister chromatids together and are cleaved, forming 2 identical daughter chromosomes
  • kinetochore microtubules shorten which pull the daughter chromosomes to opposite ends of the cell
  • polar microtubules push against each other elongating the cell
  • late stage = chromosomes reach overall maximal condensation level
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13
Q

What happend during telophase ?

A
  • microtubules lengthen, elongating cell further
  • new nuclear envelope formed around each separated daughter chromosome form membrane vesicles of parent cell’s old nuclear envelope
  • chromosomes begin to “relax” or decondense
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14
Q

Cytokinesis

A

NOT A PHASE OF MITOSIS
- Cleavage furrow (pinch) containing a contractile ring, develops where the metaphase plate used to be, pinching off the separated nuclei

  • Each daughter cell has a complete copy of the genome of its parent cell
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15
Q

Meiosis
key points

A
  • cell division of germ cells in sexually reproducing organisms to produce gametes (e.g. sperm or egg cells)
  • 2 rounds of division = 4 cells with each ONE copy oh each chromosomes (haploid)
  • paternal and maternal genetic information on chromosomes are crossed, creating new code combination on the chromosomes
  • during fertilisation, haploid cells produced by meiosis from male and female fuse = 2 copies of each chromosome again (zygote)
16
Q

Phases of meiosis

A
  • meiosis I and meiosis II divided into Karyokinesis I and Cytokinesis I and Karyokinesis II and Cytokinesis II respectively
  • same preparatory state as mitosis ( G1,S,G2)
  • Meiosis I and II are each divided into:
    Prophase
    Metaphase
    Anaphase
    Telophase
17
Q

Meiosis I - Prophase 1

A
  • longest phase
  • Homologous maternal and paternal chromosomes pair, synapse, and exchange genetic information (by homologous recombination), forming at least one crossover per chromosome
18
Q

what happens in meiosis I - prophase 1?
pt (2)

A
  • this stage in divided into series of substages names according to the apperance of chromosomes:
    1. Leptotene
    2. Zygotene
    3. Pachytene
    4. Diplotene
    DIAKINESIS
  • chromosomes condense further
  • nuclear membrane
    disintegrates into vesicles
  • meiotic spindle begins to form
  • (resembles prometaphase in mitosis)
19
Q

What happenes in
Meiosis I – Metaphase 1?

A
  • homologous pairs move along metaphase plate
  • kinetochore microtubles from both sindle poles attach to respective kinitochores
  • paired homologous chromosomes alingh=n along an equatorial plane that bisects the spindle
20
Q

what happens in Meiosis I – Anaphase 1?

A
  • Kinetochore microtubules shorten = pull homologous chromosomes to opposite poles
  • Non-kinetochore microtubules lengthen, pushing the centrosomes farther apart
  • cell elongates in separation for division down the centre
  • sister chromatids remain together
  • homologous are segregated
21
Q

Meiosis I – Telophase 1 & Cytokinesis

A
  • first meiotic division end when chromosomes arrive at the poles
  • each daughter cell had half the number of chromosomes, each chromosome has a pair of chromatids
  • cell membrane is pinched = creation of 2 daughter cells
    here, cytpkinesis isn’t fully complete, resulting in “cytoplasmatic bridges” enebling the cytoplasm to be shared betwee daughter cell untilll end of meiosis II
22
Q

Meiosis II – Prophase 2

A
  • usually involves equational segregation or separation of sister chromatids
  • disappearance of nucleoli and nuclear envelope
  • shortening and thickening of chromatids
  • centrosomes move to polar regions and arrange spindle fibres for 2nd meiotic division
23
Q

Meiosis II – Metaphase 2

A
  • Centromeres contain 2 kinetochores that attach to spindle fibres from the centrosomes at opposite poles
  • new equatorial metaphase plate is rotated by 90 degrees when compared to meiosis I – perpendicular to the previous plate
24
Q

Meiosis II – Anaphase 2

A
  • Remaining centromeric cohesin, is cleaved, allowing the sister chromatids to segregate
  • sister chromatids are now called sister chromosomes as they move toward opposing poles
25
Q

Meiosis II – Telophase 2 & Cytokinesis

A
  • De-condensation and lengthening of the chromosomes
  • disassembly of the spindle
  • Nuclear envelopes re-form and cleavage or cell plate formation eventually produces a total of 4 daughter cells, each with a haploid set of chromosomes
26
Q

stages of meiosis

A
  1. Meiosis I – Prophase 1
  2. Meiosis I – Metaphase 1
  3. Meiosis I – Anaphase 1
  4. Meiosis I – Telophase 1 & Cytokinesis
  5. Meiosis II – Prophase 2
  6. Meiosis II – Metaphase 2
  7. Meiosis II – Anaphase 2
  8. Meiosis II – Telophase 2 & Cytokinesis

Intro to Molecular Biology & Genetics (23 decks)

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