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Biology Yr 12 > DNA and Inheritance > Flashcards

DNA and Inheritance Flashcards

1
Q

What happens during nuclear division in somatic cells (mitosis and meiosis) and cytoplasmic division (cytokinesis)?

A

Eukaryotic cells pass on their instructions for growth and development from 1 generation of cell to the next.

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2
Q

How many daughter cells do mitosis and cytokinesis result in?

A

2 daughters cells (identical sets of chromosomes)

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3
Q

Define cell cycle?

A

The sequence of events from one cell division to another.

The length of the cell cycle varies in different cells

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4
Q

What are the 5 phases of mitosis?

A

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

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5
Q

What are the 3 phases in interphase?

A

G₁ phase

S phase

G₂ phase

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6
Q

What occurs during G₁ phase?

A

Cell metabolically active

Duplicates organelles and cytosolic components

Starts replicating centrosomes

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7
Q

What occurs during S phase?

A

DNA is replicated

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8
Q

What occurs during G₂ phase?

A

Cell growth continues

Enzymes and other proteins are synthesised

Replication of centrosomes is complete

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9
Q

What occurs during prophase?

A

Chromosomes condense and become visible

Spindle fibres emerge from the centrosomes

Nuclear envelope breaks down

Nucleolus disappears

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10
Q

What occurs during metaphase?

A

Mitotic spindle is fully developed

Centrosomes are at opposite poles of the cell

Chromosomes are lined up at the metaphase plate

Each sister chromatid is attached to a spindle fibre

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11
Q

What occurs during anaphase?

A

Cohesin proteins binding sister chromatids together break down

Sister chromatids (now called chromosomes) are pulled towards opposite poles

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12
Q

What occurs during telophase?

A

Chromosomes arrive at opposite poles and begin to de-condense

Nuclear envelope material surrounds each set of chromosomes

The mitotic spindle breaks down

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13
Q

What occurs during Cytokinesis?

A

Animal cells-a cleavage furrow separates daughter cells

Plant cells-a cell plate separates daughter cells

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14
Q

Define metacentric.

A

Centromere in the centre

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15
Q

Define submetacentric.

A

Centromere nearer to one end than the other

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16
Q

Define acrocentric.

A

Centromere close to one end

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17
Q

Define telocentric.

A

Centromere on the end

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18
Q

Define apoptosis.

A

Aprogrammed series of events that lead to cell death as a result of dismantling of the internal contents of the cell (DNA shredded) by various enzymes including caspases

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19
Q

Define phagocytes.

A

Scavenging cells that clear apoptotic bodies.

Particularly macrophages.

20
Q

What problems arise if apoptosis fails?

A

Cancer

Developmental defects

21
Q

What occurs during apoptosis?

A

Programmed death is signalled

Cell volume decreases

Membrane bulges outward

Nucleus fragments as cell destroys it

Apoptotic bodies form

Apoptotic debris is engulfed by macrophage

22
Q

How does cytokinesis occur in plant cells?

A

Cytoplasm of plant cells divides with the formation of a cell plate

Cellulose is deposited at cell plate forming a wall that divides the parent cell into 2 daughter cells – each with a plasma membrane

23
Q

How does cytokinesis occur in animal cells.

A

Cytoplasm divides by cleavage

Plasma membrane around the middle of cell draws together to form a cleavage furrow

Cleavage furrow continues until edges meet and cell is cleaved (results in 2 daughter cells)

May result in unequal distribution of proteins (asymetrical cell division)

24
Q

Describe binary fission.

A

Produces 2 daughter cells

Produces the same number of chromosomes as parental cell

25
Q

Why do prokaryotes undergo binary fission?

A

Lack nucleus

Single chromosome with no centromere

Not considered proper mitosis

26
Q

What occurs during binary fission?

A

DNA replicates (2 chromosomes)

Each copy attaches to a different part of the cell membrane

When cell pulls apart, original and replicate chromosomes are separated

A wall forms across the cell and divides into 2 cells of identical genetic composition

27
Q

Where does meiosis occur?

A

Specialised organs of sexually reproducing animals and plants

28
Q

What does meiosis produce?

A

Gametes (sex cells) – sperm and egg/ ova

4 daughter cells

29
Q

What occurs during prophase I?

A

Chromosomes condense, nucleolus disappears & spindle forms with centrioles at opposite ends

Homologous chromosomes lie side by side (synapsis)

A pair of chromosomes (1 maternal & 1 paternal) now called a bivalent

30
Q

What occurs during metaphase I?

A

Nuclear envelope breaks down

Homologous chromosomes move together to equator of spindle

31
Q

What occurs during anaphase I?

A

Maternal & paternal chromosomes of homologous pairs move to opposite poles of spindle.

The separation or disjunction of each pair of homologous chromosomes occurs independently

32
Q

What occurs during telophase I?

A

Spindle breaks down, cell starts to separate across its middle & nuclear envelopes form around the 2 new nuclei

33
Q

What occurs at the end of meiosis I?

A

A brief interphase

DNA does not duplicate during this interphase

34
Q

What occurs during prophase II?

A

New spindle forms at right angles to the first one

35
Q

What occurs during metaphase II?

A

Chromosomes move to equator of spindle

36
Q

What occurs during anaphase II?

A

Chromatids separate and move apart from each other

Chromatids become the chromosomes of the daughter cells

When they reach the poles, the cells enter telophase

37
Q

What occurs during telophase II?

A

Spindle apparatus disappears

Chromosomes de-condense to their thread-like form

New nuclear envelopes and nucleoli form

38
Q

Compare function of mitosis and meiosis.

A

Mitosis

  • Nuclear & cell division for growth, repair & replacement of tissues

Meiosis

  • Nuclear & cell division for producing sex cells (gametes)
39
Q

Compare the locations in which mitosis and meiosis occur.

A

Mitosis

  • Takes place in somatic cells

Meiosis

  • Takes place in gonads or reproductive organs (e.g. ovaries & testes of mammals; ovaries & anthers of flowering plants)
40
Q

Compare outputs of mitosis and meiosis.

A

Mitosis

  • Two cells are the outputs

Meiosis

  • Four cells (gametes) are the outputs
41
Q

Compare number of cell divisions in mitosis and meiosis.

A

Mitosis

  • One cell division completes the process

Meiosis

  • Two cell divisions complete the process
42
Q

Compare the number of chromosomes in each daughter cell in mitosis and meiosis.

A

Mitosis

  • Each daughter contains the diploid (2n) of chromosomes

Meiosis

  • Each daughter contains the haploid (n) of chromosomes
43
Q

Compare the way in wich organisms reproduce using mitosis or meiosis.

A

Mitosis

  • Asexually reproducing organisms reproduce by mitotic division of cells
  • Prokaryotes reproduce by binary fission not mitosis

Meiosis

  • Sexually reproducing organisms reproduce by fusion of gametes, restoring the diploid number (2n) of chromosomes of each cell
44
Q

Compare the amount of variation produced my mitosis and meiosis.

A

Mitosis

  • New cells of this kind show no variation unless mutations or environmental influences (genetically identical – clones)
  • Variation & diversity of offspring are narrowed

Meiosis

  • Offspring produced show variation between them
  • Variation and diversity of offspring are increased
45
Q

Compare the applications of mitosis and meiosis.

A

Mitosis

  • Tissue culture (skin grafts & cloning plants)

Meiosis

  • Creating new varieties of organisms

Biology Yr 12 (8 decks)

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