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Biology > Bio Unit 1.6 - Cell Division > Flashcards

Bio Unit 1.6 - Cell Division Flashcards

1
Q

What are chromosomes made out of?

A

DNA and histones

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2
Q

When do chromosomes become visible?

A

Chromatin condenses prior to cell division

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2
Q

What are two copies of a chromosome called?

A

Chromatids

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2
Q

What is the specialised region called?

A

Centromere

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3
Q

One complete set of chromosomes

A

Haploid

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4
Q

Homologous Pair

A

Chromosomes are identical and carry the same gene loci, with genes for the same characteristics

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5
Q

Diploid

A

Two complete sets of chromosomes

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6
Q

Mitosis

A

A type of cell division in which the two daughter cells have same number of chromosomes and are genetically identical to each other and parent cell

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7
Q

Three parts of mitosis and brief explanation

A

Interphase - period of synthesis and growth
Mitosis - formation of two genetically identical daughter nuclei
Cytokinesis - division of cytoplasm to form two daughter cells

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8
Q

Interphase

A

Cell grows, organelles replicate (replacing those lost in previous division), DNA replicates/doubles,

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9
Q

What happens to proteins (enzymes and histones) during interphase?

A

Synthesised, requiring energy from ATP

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10
Q

Why are the chromosomes not visible in microscope during interphase?

A

Nuclear material, chromatin, is dispersed throughout the nucleus

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11
Q

What happens to the mass of DNA during interphase?

A

Doubles

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12
Q

What happens to mass of DNA by the end of cytokinesis?

A

Halves back down

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13
Q

What are the stages of mitosis?

A

Prophase, metaphase, anaphase, telophase

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14
Q

What is the longest stage of mitosis?

A

Prophase

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15
Q

What happens to chromosomes in prophase?

A

chromosomes condense and coil and become visible as long thin threads (distinguishable as a pair of chromatids)

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16
Q

What happens to centrioles during prophase?

A

Pairs separate and move to opposite poles of cells, organising a partner as they move. When they reach opposite poles they are in pairs again

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17
Q

What forms during prophase?

A

Protein microtubules form making a spindle . Spindle fibres extend from pole to pole to the centromere of each chromosome.

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18
Q

What happens toward the end of prophase?

A

Nuclear envelope disintegrates and nucleolus appears

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19
Q

Where can pairs of chromatids be seen freely in prophase?

A

Cytoplasm

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20
Q

What happens to the chromosomes at metaphase?

A

Each pair of chromosome is a pair joined at the centromere, centromere attaches to spindle fibres so chromosomes are aligned on the equator

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21
Q

What form do the chromosomes take in metaphase?

A

Line

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22
Q

What happens during anaphase?

A

Rapid stage, spindle fibres shorten and centromeres separate, pulling chromatids to the poles

23
Q

When does telophase happen?

A

When chromatids have reached the poles of the cells

24
Q

What happens to chromosomes in telophase?

A

Uncoil and lengthen

25
Q

What happens to spindle fibres in telophase?

A

Break down

26
Q

What happens to nuclear envelope in telophase?

27
Q

What happens to nucleolus in telophase?

28
Q

What is cytokinesis?

A

The division of cytoplasm to make two cells

29
Q

How does cytokinesis occur in animal cells?

A

Constriction of parent cell around equator from the outside inward (cleavage furrow)

30
Q

How does cytokinesis occur in plant cells?

A

A cell plate forms across equator of parent cell from centre outwards and they join to form a new cell wall

31
Q

Spindle difference between animal and plant cells?

A

AC - degenerates at telophase
PC - remains throughout new cell wall formation

32
Q

Shape change in cytokinesis AC and PC

A

AC - cell becomes rounded before mitosis
PC - no shape change

33
Q

Why is mitosis important for growth?

A

Replicates cells that can form tissues to replace worn away tissues

34
Q

Where does mitosis occur in plant cells and animal cells

A

PC - meristems
AC - bone marrow/epithelia

35
Q

How do genes act as a control?

A

Prevents cell cycle from repeating continually. Genes are called “tumour suppressor genes”

36
Q

Proto-oncogene

A

A gene which when mutated becomes an oncogene and contributes to the development of cancer

37
Q

Oncogene

A

A gene which causes uncontrolled cell division

38
Q

Where does meiosis take place and what does it produce?

A

Reproductive organs and results in four genetically distinct haploid gametes

39
Q

How many divisions does meiosis have?

40
Q

Mass of DNA throughout meiosis?

A

Doubles during S Phase, halves after meiosis 1 and halves again after meiosis 2

41
Q

What happens during meiosis 2?

A

Chromatids separate. Each daughter cell has half number of chromosomes (each with only one chromatid)

41
Q

What happens during meiosis 1?

A

Homologous pairs separate. Each daughter cell has half chromosomes (each chromosome comprises of 2 chromatids.)

42
Q

What happens to chromosomes and spindle in Prophase 1?

A

Chromosomes condense, centrioles separate and move to different poles, centrioles organise the polymerisation of microtubules and spindle forms.

43
Q

How is Prophase 1 different to mitosis prophase?

A

Homologous chromosomes associate in bivalents, chromatids wrap around each other and partially repel each other, joined at the chiasmata

44
Q

What happens at the chiasma during Prophase 1?

A

Segment of DNA of one chromatid exchanged for another part of DNA from homologous chromosome (genetic variation.) This produces a new set of alleles

45
Q

What happens to nuclear envelope in prophase and nucleolus?

A

Nuclear envelope disintegrated and nucleolus disappeared

46
Q

What happens during metaphase 1?

A

Pairs of homologous chromosomes arrange themselves at equator of spindle randomly. Independent assortment takes place (combination of chromosomes going into daughter cell is mix of paternal and maternal chromosomes)

47
Q

What happens during anaphase 1?

A

Chromosomes in each bivalent separate and spindle fibres shorten, one of each pair pulled to opposite poles. Random mixture of maternal and paternal chromosomes

48
Q

What happens during telophase?

A

Nuclear envelope reforms, chromosomes decondense sometimes

49
Q

How is meiosis 1 different to meiosis 2?

A

Chromatids rather than chromosomes that are separating at anaphase

50
Q

What happens at prophase 2?

A

Centrioles separate and organise a new spindle at right angles to old spindle

51
Q

What happens at metaphase 2?

A

Chromosomes line up on the equator with each chromosome attached to a spindle fibre by its centromere. Independent assortment takes place

52
Q

What happens at anaphase 2?

A

Spindle fibres shorten and centromeres separate, pulling chromatids to opposite poles

53
Q

What happens at telophase 2?

A

At the poles, chromatids lengthen, spindle disintegrates and nuclear envelope and nucleolus reform

54
Q

What does cytokinesis produce in meiosis 2?

A

4 haploid daughter cells

55
Q

How does meiosis produce genetically different haploid daughter cells?

A

Closing over during prophase 1 and independent assortment during metaphase 1 and 2 (different combinations of maternal/paternal chromosomes and different chromatids)

56
Q

Why is variation essential?

A

To survive in a constantly changing environment and to colonise new ones

Biology (10 decks)

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