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Biological Systems > Chapter 7 Cell Division > Flashcards

Chapter 7 Cell Division Flashcards

1
Q

What are the 2 basic strategies for reproduction?

A

Asexual and sexual

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2
Q

How does diversity occur in asexual reproduction

A

Asexual reproduction creates clones. Diversity comes from mutations or environmental factors

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3
Q

What are different methods of asexual reproduction

A

Single cell prokaryotes - binary fission
Single cell eukaryotes - mitosis and cytokinesis
*mutlicellular eukaryotes can reproduce asexually too

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4
Q

What does Sexual reproduction involve

A

involves fusion of gametes (form by meiosis which reduces genetic material by half)
leads to genetic variation

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5
Q

What are somatic cells

A

cells not specialized for reproduction

- contain 2 sets of chomosomes in homologous pairs (one from female and one from male parent)

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6
Q

How are gametes different to somatic cells

A

Only have one set of chomosomes - one homolog from each pair of parent cell
Are haploid; number of chom osomes = n

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7
Q

What is fertilization

A

2 haploid gametes form zygote

diploid; number of chomosomes = 2n

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8
Q

What are the 4 events in cell division

A

Reproductive signals
DNA replication
DNA segregation - distribution of DNA into 2 new cells
Cytokinesis - division of cytoplasm and separation of two new cells

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9
Q

How do prokaryotes reproduce

A

Binary fission - results in reproduction of the entire organism
Reproductive signal may be environmental factor such as nutrient availability

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10
Q

How does DNA replication occur in prokaryotes

A

Most prokaryotes have one circular chomosome with 2 important regions
- ori- (replication starts)
- ter - (replication ends)
DNA replicates when threaded through replication complex of proteins in centre of cell

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11
Q

How does segregtaion occur in prokaryotes

A

during replication ori complexes move to opposite end of cell, their adjacent DNA sequences bind proteins for segregation using ATP
- Actin-like protein provides filament for ori and other proteins to move

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12
Q

How does cytokinesis occur in prokaryotes

A

after segregation cell membrane pinches by contraction of ring of protein fibers under surface - new ell wall materials are deposited resulting in 2 separate cells

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13
Q

How do eukaryotic cells divide?

A

Mitosis followed by citokinesis

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14
Q

How is cell division different in eukaryotic cells

A

Signals are usually related to organism function, not individual cell
- most cells in multicellular organisms are specialised and do not divide
DNA replication - DNA replicated as threaded through replication complexes (same) only occurs at specific stage of cell cycle
DNA segregation - more complex due to nuclear envelope and multiple chromosomes
Cytokineses - different in animal cells due to lack of cell wall (same in plant cells)

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15
Q

What is the cell cycle

A

period from 1 cell division to the next

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16
Q

What are the 2 main phases of the cell cycle

A

M phase: Mitosis followed by cytokinesis

Interphase: cell nucleus is visible and cell functions occur (including DNA replication)

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17
Q

What are the 3 subphases of interphase

A

G1 (Gap 1): Specialized cell function, variable duration
S (synthesis): DNA repliction
G2 (Gap 2): cell prepares for mitosis, synthesizing microtubules for segregating chromosomes

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18
Q

What are the stages of mitosis

A

Prophase - metaphase - anaphase - telophase

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19
Q

What occurs during prophase

A

3 structures appear

  • Condensed chromosomes (chromosomes after recplicating have 2 dna molecules called ‘sister chromatids’ joinded at the centromere)
  • reorient chromosomes (centrosomes determine orientation of spindle. S phase centrosomes duplicate, G2-M phase centrosomes move toward opposite sides of nucleus)
  • Spindle (forms between poles formed by centrosomes)
20
Q

What do microtubules do during Spindle part of prophase

A

Polar microtubules - overlap in middle region, keep poles appart
Astral microtubules - interact with cell membrane proteins, also keep poles apart
Knetochore microtubules - attache to kinetocores on chromatid centromeres, pull sister chromatids to opposite sides

21
Q

what is the difference between chromatids and chromosomes

A

Chromatids - share centromere

Chromosome - own centromere

22
Q

What are the strops of mitosis between prophase and telophase?

A

Prometaphase - nuclear envelope breaks down, chromatids attach to kinetochore microtubules
Metaphase - chromosomes line up in middle of cell
Anaphase - chromatids separate towards pole

23
Q

What is the difference between mitosis and meiosis?

A

Meiosis has 2 rounds of cell division and produces 4 haploid cells
Mitosis has one round of cell division and produces 2 genetically identical diploid cells

In both the DNA only replicates Once

24
Q

What is the mechanism for daughter chromosome movement towards the poles in anaphase?

A

Kinesin and Dyenin (molecule motor proteins) move chromosomes along kinetochore microtubles that also shorten towards the poles

25
Q

What occurs during telophase?

A

Last phase of mitosis, where nuclear envelope forms around each set of chromosomes and nucelioli appears
Spindle breaks and chromosomes become less compact

26
Q

What is the karyotype

A

Description of condensed chromosome size and centromere position

27
Q

How does cytokinesis occur in animal cells?

A

Cell membrane pinches in between the nuclei

Actin and Myosin ring forms on inner cell membrane surface

28
Q

How does cytokinesis occur in plant cells?

A

Vesicles form golgi apparatus appear along plane of cell division - fuse to form new cell membrane
- Vesicles contents contribute to cell plate (beginning of new cell wall)

29
Q

What stage of mitosis allows eukaryotic cells to control reproduction?

A

G1-S transition is the restricted point

growth factors stimulate transition. Passing the S phase usually leads to cell division

30
Q

What is the the trigger substance that allows progression through phases in mitosis?

A

Cyclin-dependent Kinases (CDKs)

They function at cell cycle checkpoints and signal for cell to proceed to next phase

31
Q

What causes checkpoints in the phases of mitosis?

A

G1 - triggered by DNA damage
S - triggered by DNA damage or incomplete replication
G2 - triggered by DNA damage
M - triggered by chromasome to spindle attachment failure

32
Q

What triggers the activation of CDKs?

A

Each CDK has own cyclin to activate it which is broken down into prodease after action.
Growth factors and various signals trigger cyclin synthesis

33
Q

Why is meiosis used for producing gametes

A

Because it produces genetically different cells to the partent cell

34
Q

What is the function of Meiosis

A

Reduce chromosome numbers form diploid to haploid
Ensure haploid cells have full set of chromosomes
Promote genetic diversity

35
Q

What is the purpose of crossing over in Meiosis and when does it occur?

A

Homologous pairs of chromosomes line up along lengths (4 chromatids)
They repel at centromeres but remain attached at chiasmata
Genetic material is then exchagned between nonsister chromatids at chiasmata -> recombinant chromatids

Occurs during prophase 1 (prophase of first meiosis)

36
Q

What are the 2 processes that allow for shuffling of genetic material in meiosis?

A

Crossing over and Independent assortment

37
Q

What is independent assortment and when does it occur

A

Occurs during anaphase 1
Chance determines which member of a homologous pair goes into which daughter cell
In humans therear e 2^23 possible cominations

38
Q

What are potential errors that can occur in meiosis

A

Nondisjunction
Polyploidy
Translocation

39
Q

What is nondisjucntion

A

When homologous pairs fail to separate at anaphase 1 or sister chromatids don’t separate at anaphase 2
- Causes Aneuploidy (abnormal chromosome number)

40
Q

WHat is polyploidy

A

Organisms with triploid (3n) or tetraploid (4n) or > chromosomes
0 Due to additional DNA replication before meiosis or lack of spindle in meiosis II
- occurs naturally for some species

41
Q

What is Translocation

A

crossing over of nonhomologous chromosomes in Meiosis 1

Can affect gene expression

42
Q

What is a dangerous case of translocation

A

Translocation of chromosomes 9 and 22 can cause leukaemia

43
Q

What are the 2 mechanisms of cell death

A

Apoptosis - programmed

Necrosis - due to damage or nutrient starvation

44
Q

What is the process of apoptosis

A

Cell detaches from neighbours
DNA cut into fragments
Membranous loves form, break into fragments

45
Q

What are reasons for apoptosis

A

cell no longer needed (e.g. connective tissue between fingers of foetus
Cell is old and prone to genetic damage
Surrounding cells usually ingest dead cells via phagocytosis

46
Q

How is apoptosis controlled

A

Controlled by signals
- Internal signals related to cell age or DA damage
-Internal and external signals lead to activation of caspases - which hydrolyze target proteins
Cell dies when caspases hydrolyze proteins in nuclear envelope, nucleosomes and cell membrane

47
Q

How does necrosis cause inflammation?

A

Cell contents are released - triggers inflammatory mediators

Biological Systems (20 decks)

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