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OCR Biology AS H020 > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

What are the 2 main phases of the cell cycle in eukaryotic cells?

A

Interphase and mitotic (division) phase.

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2
Q

Which phase does a cell spend the majority of its time?

A

Interphase.

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3
Q

What happens in G1?

A

Cellular contents are duplicated, new proteins and organelles are made, the cell grows.

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4
Q

What happens in S?

A

The cell replicates its DNA in the nucleus.

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5
Q

What happens in G2?

A

The cell continues to increase in size, energy stores are increased, the proteins needed for division are made, the duplicated DNA is checked for errors.

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6
Q

What happens in M?

A

This is the mitotic phase (including cytokinesis).

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7
Q

What happens in G0?

A

The cell leaves the cycle (temporary or permanent) due to differentiation (no longer able to divide), DNA damage ( no longer viable - permanent cell arrest) or lymphocytes (which can return).

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8
Q

Where do checkpoints occur in the cell cycle?

A

After G1, G2 and M.

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9
Q

What happens in the G1 checkpoint?

A

The cell is checked for cell size, nutrients, growth factors and DNA damage.

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10
Q

What happens in the G2 checkpoint?

A

Checks the DNA has been copied correctly.

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11
Q

What happens in the metaphase checkpoint?

A

Spindle assembly checkpoint where all spindles are checked to see if they are attached to chromosomes and have aligned.

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12
Q

What is the difference between mitosis and cytokinesis?

A

Meiosis is where the nucleus divides, cytokinesis is when the cytoplasm divides and two cells are produced.

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13
Q

What is the cell cycle?

A

A highly ordered sequence of events that takes place in a cell, resulting in division of the cell and the formation of two genetically identical daughter cells.

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14
Q

What is asexual reproduction?

A

The production of genetically identical offspring from one parent in multicellular organisms.

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15
Q

What organisms reproduce by asexual reproduction?

A

Plants, fungi, some animals and single called eukaryotes (amoeba).

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16
Q

How do prokaryotes (bacteria) asexually reproduce?

A

Binary fission.

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17
Q

What are two identical DNA molecules called?

A

Chromatids

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18
Q

Where are two chromatids joined together?

A

A middle region called the centromere.

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19
Q

What happens in prophase?

A

Chromosomes condense getting shorter and fatter. Centrioles move to opposite poles (absent in plant cells). Spindle apparatus begins to form. The nuclear envelope breaks down. Chromosomes lie free in the cytoplasm. Chromosomes move towards the equator.

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20
Q

What happens during metaphase?

A

Chromosomes line up along the equator, they become attached to the spindle by the centromere. Metaphase checkpoint occurs.

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21
Q

What happens during anaphase?

A

Microtubules contract causing individual chromosomes to superset and move to opposite poles. Chromatids move rapidly using energy from mitochondria.

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22
Q

What happens during telophase?

A

Chromosomes uncoil and become long and thing. Spindle fibres disintegrate and the nuclear envelope forms.

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23
Q

What happens during cytokinesis?

A

The cytoplasm divides in animal cells. A cleavage furrow forms to divide the cell membrane.

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24
Q

Normal cells have two chromosomes of each termed _____ one from each parent.

A

Diploid

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25
Q

What are sex cells called?

A

Gametes

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26
Q

What is a fertilised egg called?

A

Zygote.

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27
Q

How are gametes formed?

A

Meiosis

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28
Q

Explain the term haploid…

A

A gamete contains half of the chromosome number of the parent cell.

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29
Q

Meiosis is also known as…

A

Reduction division

30
Q

What are homologous chromosomes?

A

Matching sets of chromosomes with the same genes at the same loci.

31
Q

What are alleles?

A

Different versions of the same gene (gene variants)

32
Q

What happens during prophase 1?

A

Chromosomes condense getting shorter and fatter. The nuclear envelope breaks down. The spindle apparatus begins to form. Homologous chromosomes pair up forming bivalents. Crossing over occurs. Centrioles move to opposite poles. Chromosomes lie free in the cytoplasm.

33
Q

What happens during metaphase 2?

A

Homologous pairs line up along the equator/metaphase plate randomly (independent assortment), they become attached to the spindle by the centromere. Metaphase checkpoint occurs.

34
Q

What happens during anaphase 1?

A

Homologous chromosomes are pulled to different poles, chromatids stay joined together, microtubules contract using energy from mitochondria. Chaismata occurs where DNA breaks of and rejoins between sister chromosomes.

35
Q

What happens in telophase 1?

A

It is identical to telophase.

36
Q

Define differentiated…

A

Specialised to carry out a specific function

37
Q

Describe and explain the differentiation of erythrocytes…

A

Flattened bacon cave disc to have a large SA:V for exchange. No nucleus to leave more room for haemoglobin. Small and flexible to squeeze through capillaries.

38
Q

Describe and explain the differentiation of neutrophils…

A

Multilobed nucleus for more flexibility to get to sites of infection. Granular cytoplasm as there are many lysosomes with hydrolytic enzymes.

39
Q

Describe and explain the differentiation of sperm cells…

A

Flagellum for movement. Many mitochondria to supply energy. Across me has digestive enzymes to penetrate and fertilise the egg.

40
Q

Describe and explain the differentiation of palisade cells…

A

Many chloroplasts for photosynthesis. Large vacuole to maintain turgor. Thin cell walls for faster rates of diffusion. Chloroplasts can move in the cytoplasm to gain more light. Regular rectangle to pack closely.

41
Q

Describe and explain the differentiation of root hair cells…

A

Large SA:V for absorption. Thin cell wall for diffusion/osmosis. Mitochondria for active transport.

42
Q

Describe and explain the differentiation of guard cells…

A

Thick inner walls so it bends outwards.

43
Q

Describe and explain the differentiation of squamous epithelium…

A

One cell think for rapid diffusion. Large SA:V, regular layer all for diffusion.

44
Q

Describe and explain the differentiation of ciliated epithelium…

A

Cilia for external movement. Goblet cells to secrete mucus.

45
Q

Describe and explain the differentiation of cartilage tissue…

A

Elastin and collagen so it’s firm and flexible. It is formed when chloroblasts secrete an extracellular matrix which they become trapped inside.

46
Q

Describe and explain the differentiation of muscle…

A

It can be skeletal, cardiac or smooth. Skeletal muscle fibres contain microfibrils with contractile proteins for contraction.

47
Q

Describe and explain the differentiation of phloem…

A

Sieve tube cells for separation by perforated walls, companion cells for life support.

48
Q

Describe and explain the differentiation of xylem…

A

Walls are strengthened by lignin for structural support. Living parenchyma cells fill in the gaps between dead vessels.

49
Q

What is a tissue?

A

A collection of differentiated cells that have a specialised function

50
Q

What are the 4 categories of tissues in animals?

A

Nervous, epithelial, muscular and connective.

51
Q

Name 2 plant tissues…

A

Epidermis and vascular.

52
Q

What is an organ?

A

A collection of tissues that are adapted to perform a particular function in an organism.

53
Q

Name 3 organ systems in animals…

A

The digestive system, the cardiovascular system, the gaseous exchange system.

54
Q

The process of a spell becoming specialised is called?

A

Differentiation which involves the expression of some genes and not others.

55
Q

Undifferentiated cells are called?

A

Stem cells.

56
Q

What phase of the cell cycle do cells enter when they become specialised?

A

G0

57
Q

Uncontrolled cell division is also known as a….

A

Cancerous tumour.

58
Q

Define potency…

A

The ability to differentiate into different cell types.

59
Q

Define totipotent…

A

Can differentiate into any type of cell.

60
Q

Give examples of totipotent cells…

A

Fertilised eggs or zygotes.

61
Q

Define pluripotent…

A

Stem cells that can form all tissue types but not whole organisms.

62
Q

Give an example of a pluripotent cell…

A

Early embryos - blastocysts

63
Q

Define multipotent…

A

Stems cells that can form only a range of cells within a certain type of tissue.

64
Q

Give examples of multipotent stem cells…

A

Haematopoetic stem cells in bone marrow.

65
Q

What is the lifespan of a erythrocyte?

A

120 days

66
Q

Why do erythrocytes have a short lifespan?

A

Due to their lack of a nucleus and organelles.

67
Q

What is the lifespan of a neutrophil?

A

6 hours

68
Q

Where are stem cells present in plants?

A

Meristematic tissue

69
Q

Where is meristematic tissue found in plants?

A

Growth regions and between the xylem and phloem (vascular cambium).

70
Q

Where are stem cells already used?

A

The treatment of burns, developmental biology and drug trials.

71
Q

Which diseases do stem cells have the potential to treat?

A

Heart disease, type 1 diabetes, Parkinson’s, Alzheimer’s, macular degeneration, birth defects and spinal injuries.

OCR Biology AS H020 (10 decks)

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