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Cell Division Flashcards

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1
Q

What is Cell Division? Karyokinesis ? Chromosomes? Chromatids?

What does it function in?

What is it in diploid cells

A

Cell division is nuclear division(karyokinesis) followed by cytokinesis.

It functions in growth, repair, reproduction.

In diploid cells, there are two copies of every chromosome, forming a pair(homologous chromosome)

Humans have 46 chromosomes, 23 homologous pair, a total of 92 chromatids.

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2
Q

MTOCs

Describe what it is and name 2 functions

A

Microtubule organizing centers aka centrosomes. Pair of these lay outside nucleus.

2 main functions: the organization of eukaryotic flagella and cilia and the organization of the mitotic and meiotic spindle apparatus, which separate the chromosomes during cell division.

In animal cells, each MTOC contains a pair of centrioles.

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3
Q

Mitosis:

Prophase

What breaks down? What forms?

A

Prophase: nucleus disassembles: nucleolus disappears, chromatin condenses into chromosomes, and nuclear envelope breaks down.

Mitotic spindle is formed.

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4
Q

Mitosis:

Metaphase

What is each chromosome complete with?
What forms at the opposite side?

A

Chromosomes line up in single file at the center

Centrosomes at opposite ends of cell.

Spindle fibers run from the centrosomes to the kinetochores in the centromeres.

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5
Q

Mitosis:

Anaphase

Disjunction?

A

Microtubules shorten, each chromosome is pulled apart into two chromatids(once separated, chromosomes double) Pulls chromosomes to opposite poles(disjunction); at the end of this phase, each pole has a complete set of chromosome, same as original cell before replication.

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6
Q

Mitosis:

Telophase

A

Nuclear division, nuclear envelop develops, chromosomes —-> chromatin, nucleoli reappear.

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7
Q

Mitosis: Telophase—cytokinesis

A

Actually begins in later stages of mitosis(end of anaphase). Division of cytoplasm to form 2 cells.

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8
Q

Mitosis: Cyokinesis—-cleavage furrow

A

In plant cells, it Forms down the middle of a cell. Actin and myosin microfilaments shorten, pull plasma membrane into center(animal)

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9
Q

Mitosis: Cytokinesis - Cell Plate

A

In plant cells, a cell plate forms during telophase as vesicles from the Golgi go straight down the middle of the cell.

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10
Q

Interphase

A

Begins after mitosis and cytokinesis are complete

Cell cycle= M,G1, S, G2 phases

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11
Q

Interphase: What is S phase?

Where is more time spent in? Mitosis/Interphase

A

During S phase, second molecule of DNA replicated from the first, provides sister chromatids.

More time spent in interphase than mitosis(>90%) Growth occurs in all 3 interphases, not just G’s.

During G2, material for next mitotic division are prepared.

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12
Q

When are the checkpoints in Interphase?

A

Near the end of G1 - cell growth assessed and favorable conditions checked. If fails, cells enters G0.

End of G2- checks for sufficient Mitosis Promoting Factor (MPF) levels to proceed.

M checkpoint during mitosis that triggers start of G1.

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13
Q

Meiosis I:

A

Also called the reduction division. In this process. homologous chromosomes separate.

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14
Q

Meiosis:

Prophase I

A

Nucleus disassembles: nucleolus disappears and nuclear envelop breaks down, chromatin condenses, spindle develops. MT’s begin attaching to kinetochores. Crossing over means genetic recomb.

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15
Q

Meiosis:

Prophase I – Synapsis, Chiasmata, Synaptonemal complex

A

Synapsis: aka Tetrad. The pairing of homologues occurs.

Chiasmata: Visiable manifestations of cross-over events occur.

Synaptonemal complex: protein structure that temporarily forms between homologous chromosomesL gives rise to the tetrad w/ chiasmata and crossing over.

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16
Q

Meiosis:
Describe 5 steps in Prophase I

  1. Leptotene
  2. Zygotene
  3. Pachytene
  4. Diplotene
  5. Diakinesis
A
  1. Leptotene- chromosomes start condensing
  2. Zygotene- Synapsis begins; synaptonemal complex forming)
  3. Pachytene - Synapsis complete, crossing over
  4. Diplotene - synatopnemal complex disappears, chiasma still present.
  5. Diakinesis - nuclear envelop fragments, chromosomes complete condensing, tetrads for ready for metaphase.
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17
Q

Meiosis - Metaphase I:

A

homologous pairs of chromosomes line up in double file along the plate.

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18
Q

Meiosis - Anaphase I

A

Homologoues chromosomes are pulled by spindle fibers to opposite sides (disjunction)

19
Q

Meiosis - Telophase I

A

Nuclear membrane develops. Each pole forms a new nucleus that has half number of chromosomes( from homologous pair to each chromosome = 2 sister chromatids)

Chromosomes reduction phase to haploid.
- Interphase may occur in between here, depending on the species.

20
Q

Meiosis II

A

The same are Mitosis. Each parent cell contains four chromosomes.

21
Q

Meiosis - Prophase II

A

Nuclear envelop disappears and spindle develops etc., no chiasmata and no crossing over.

22
Q

Meiosis- Metaphase II

A

Chromosomes pair up and align on plate like in mitosis but now with half number of chromosomes (no extra copy)

23
Q

Meiosis - Anaphase II

A

Each chromosome is pulled into 2 separate chromatids by microtubles of the spindle apparatus.

24
Q

Meiosis - Telophase II

A

Nuclear envelop reappears and cytokinesis occurs —-> habloid cells( each chromosome = 1 chromatid)

25
Q

Mitosis is for ____ cells

Meiosis is for ____ cells

A

Mitosis is in somatic cells

Meiosis in gametes(egg, sperm, pollen)

26
Q

Genetic Variation: Genetic recombination during meiosis and sexual reproduction originates from 3 events:

A
  1. Crossing over during prophase I
  2. Independent assortment of homologous during metaphase I ( which chromosomes goes into which cell)
  3. Random joining of gametes aka germ cells(which sperm fertilizes which egg - genetic composition of gamete affects this)
27
Q

Regulation of Cell Cycle:

  1. Surface-to-volume ratio (S/V)
A

Volume gets much larger when cells grow. When S/V is large, exchange becomes much easier. When S/V is small, exchange is hard, leads to cell death or cell division to increase SA.

28
Q

Regulation of Cell Cycle:

  1. Genome-to-volume ratio (G/V)
A

Genome size remains constant throughout life; as cell grows, only volume increases.

G/V will be small and thus exceed the ability of its genome to produce sufficient amounts of regulator of activities. Some large cells(paramecium, human skeletal muscle) are multi-nucleated to deal with this.

29
Q

Checkpoints: cell specific regulations

1.G1 checkpoint

A

aka restriction point, the most important one. At the end of G1 phase, if cell is not ready to divide it may act here (G0 phase - nerve and muscle cells remain here, rarely divide after maturing) and never proceed or wait until it is ready.

30
Q

Checkpoints: cell specific regulations

  1. G2 checkpoint:
A

End of G2 phase, evaluates accuracy of DNA replication and signal whether to begin mitosis.

31
Q

Checkpoints: cell specific regulations

  1. M checkpoint
A

During metaphase, ensures microtubules are properly attached to all kinetochores.

32
Q

Cyclin-dependent kinases (Cdk’s)

A

Cdk enzyme activates proteins that regulate cell cycle by phosphorylation; Cdk’s are activated by protein cyclin.

33
Q

Growth factor:

A

Plasma membrane has receptors for growth factors that stimulate cell for division(such as damaged cell)

34
Q

Density-dependent inhibition:

A

Cells stop dividing when surrounding cells density reaches maximum.

35
Q

Anchorage dependence:

A

Most cells only divide when attached to an external surface such as neighboring cells or side of culture dish.

-Cancer cells defied all of the 5 conditions above( such cells are called TRANSFORMED cells)

36
Q

At anaphase of mitosis, there would be a total of _____ chromosome/chromatids if a cell has ____ chromosomes at beginning. Even when pulled apart of sister chromatids, each one is now a complete chromosome.

A

At anaphase of mitosis, there would be a total of 92 chromosome/chromatids if a cell has 46 chromosomes at beginning. Even when pulled apart of sister chromatids, each one is now a complete chromosome.

37
Q

At anaphase I, there would be a total of ___ chromosomes if a cell has ___ chromosomes at beginning because ___ chromosomes are pulled to each pole by independent assortment and no chromatids are separated at anaphase I.

A

At anaphase I, there would be a total of 46 chromosomes if a cell has 46 chromosomes at beginning because 23 chromosomes are pulled to each pole by independent assortment and no chromatids are separated at anaphase I.

38
Q

Do plants have centrioles?(formation of cell plate)

A

Plants do not have centrioles.

39
Q

Is mitosis a genetic variation?

A

Mitosis = no genetic variations.

40
Q

Where does meiosis occur in?

A

In sexually reproducing organisms and the results are cells that are haploids.

41
Q

In meiosis, a replicated chromosome consists of _____

A

two sister chromatids, where one is an exact copy of the other.

42
Q

A kinetochore is______

A

a disc-shaped protein on the centromere that attaches the chromatid to the mitotic spindle during cell division.

43
Q

Alternation of Generations:

Describe them

A

Gametophyte(n) ——>Mitosis—–> Makes Gametes(n) —->Fertilization—->Sporophytes(2n) —–>Meiosis——>Spores(n)
—>Mitosis—–>Gametophyte

Biology (24 decks)

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