SB2: Cells And Control Flashcards

1
Q

Name the two stages of the cell cycle

A

Interphase and mitosis

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2
Q

List the five stages of mitosis in order

A
  • prophase
  • metaphase
  • anaphase
  • telophase
  • cytokinesis
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3
Q

Describe what happens during interphase

A

The stage when the cell prepares itself for the process of cell division, and DNA replication takes place. The cell also makes more of its sub-cellular structures, and increases in size

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4
Q

Describe what happens during each stage of mitosis

A

Prophase: the nucleus starts to break down and spindle fibres appear
Metaphase: the chromosomes line up across the middle of the cell
Anaphase: the separated chromosomes move away from each other
Telophase: the chromosomes arrive at opposite ends of the cell and the nucleus membrane reforms
Cytokinesis: the cytoplasm of the cell is separated as the cell membrane is pinched to divide the cell into two daughter cells

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5
Q

Why is mitosis important for an organism?

A

It is a process of producing genetically identical, diploid cells, needed for growth

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6
Q

What do we call cells that have one copy of each chromosome?

A

Haploid

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7
Q

Name three examples of a cell with only one copy of each chromosome

A

Gametes: egg, sperm, pollen

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8
Q

What do we call cells that have two copies of each chromosome?

A

Diploid

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9
Q

Name an example of a cell with two copies of each chromosome

A

Any body cell (eg. Muscle, epithelial, nerve etc.)

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10
Q

Fruit flys have four types of chromosomes. How many chromosomes are in a diploid fruit fly cell?

A

8

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11
Q

Explain why the number of mitochondria in a cell doubles during interphase

A

So each daughter cell has enough mitochondria/ same number of mitochondria as parent cell

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12
Q

What do we call the offspring from asexual reproduction?

A

Clones

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13
Q

What are spindle fibres and what is their function?

A

Filaments formed in a cell during mitosis, which help to separate chromosomes

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14
Q

Give a benefit of asexual reproduction

A
  • produces clones
  • doesn’t need two parents
  • fast method of producing offspring
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15
Q

Give a disadvantage of asexual reproduction

A
  • does not provide variation, so a whole population could get killed by one disease
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16
Q

Describe how mitosis produces genetically identical, diploid cells

A

The cell copies each chromosome to produce two sets. Each set of chromosomes move to opposite sides of the cell. The cell then splits into two cells, each with a full set of identical chromosomes

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17
Q

Why is each plantlet that grows along a strawberry runner a clone?

A

Because they are genetically identical to the parent plant/ have the same chromosomes (/DNA/genes) as the parent plant

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18
Q

How can cancers grow?

A

The cell cycle goes out of control

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19
Q

Describe what a ‘crown gall tumour‘ on a rose plant will look like?

A

A lump (often brown) on the stem

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19
Q

Explain how crown gall tumours develop

A

There is a change to the cells that causes rapid and uncontrollable cell division

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20
Q

What is the definition of growth?

A

An increase in size due to an increase in the number or size of cells

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21
Q

What are percentile curves used for?

A

The graph shows the expected rate of growth of babies of different birth weights and is used to check that a child‘s growth is normal

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22
Q

What are the three zones of growth in plants?

A
  • zone of cell division (meristem)
  • zone of elongation
  • zone of differentiation
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23
Q

Name the two types of stem cells in animals

A

Embryonic stem cells and adult stem cells

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24
Q

Describe the differences between the two types of animal stem cells

A

Embryonic stem cells can produce any type of specialised cell whilst adult stem cells can only produce the type of specialised cell that is in the tissue around them

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25
Q

Give three advantages of using stem cells to treat people

A

(1) no need to take anti-rejection drugs because cells are genetically identical
(2) no need to find a donor
(3) no need for tissue typing

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26
Q

Give some disadvantages of using stem cells to treat people

A

(1) the stem cells may cause cancer if they continue to divide inside the body after they have replaced the damaged cells
(2) cultured stem cells could be contaminated with viruses which would be transferred to a patient
(3) no guarantees that the therapy will be successful
(4) lack of stem cell donors
(5) hard to obtain and store a person‘s embryonic stem cells - need to be collected near the start of the pregnancy

27
Q

What are the ethical problems of using stem cells to treat people or during research?

A
  • one source of embryonic stem cells is unused embryos produced by ‘in vitro fertilisation‘ (IVF)
  • is it right to create embryos for therapy, and destroy them in the process?
  • embryos could come to be viewed as a commodity (item), and not as an embryo that could develop into a person
  • when should an embryo be regarded as, and treated as, a person?
28
Q

What are plant stem cells called?

A

Meristem cells

29
Q

Name two parts of a plant where stem cells can be found

A
  • roots

- shoots

30
Q

What are chromatids?

A

The product produced when chromosomes replicate

31
Q

What cells is mitosis unlikely to occur in?

A
  • sperm/egg cell (gametes)
  • red blood cell
  • lymphocyte
32
Q

Which structures of a flowering plant give rise to potatoes?

A

A potato is a tuber formed at the end of an underground stem

33
Q

Which structures of a flowering plant give rise to the fleshy scales of an onion?

A

Onion scales are modified leaves containing a food store

34
Q

In the process of tissue culture in plants, what is needed to induce the formation of a complete plant, in addition to a growth medium with nutrients?

A

The appropriate plant growth substances (‘hormones‘) would need to be added

35
Q

List four stimuli which can be detected by the skin

A
  • heat
  • cold
  • touch
  • pressure
36
Q

How do we become aware of a stimulus?

A

Nerve impulses travel from a receptor to the brain

37
Q

Name the transparent outer layer found at the front of the eye

A

Cornea

38
Q

What is the retina?

A

It is the layer at the back of the eye that contains light receptor cells

39
Q

What is the pupil?

A

It is the hole in the centre of the eye through which light enters

40
Q

What is the iris?

A

The part of the eye that contains muscles that control the size of the hole in the centre of the eye

41
Q

Name the muscles that control the shape of the lens

A

Ciliary muscles

42
Q

Name the nerve that takes information from the eye to the brain

A

Optic nerve

43
Q

What happens to the optic nerve when a bright light shines in the eye?

A

Impulses travel in the optic nerve

44
Q

When a bright light shines in the eye, do the radial fibres in the iris contract?

A

No, the circular muscles in the iris contract to make the pupil smaller (in dim light the radial muscles contract to make the pupil larger)

45
Q

What responds when a bright light shines in the eye?

A

The retina

46
Q

What is the cause of the blind spot in the field of vision?

A

There are no sensory cells in the blind spot

47
Q

Which parts of the eye refract the light to form an image on the retina?

A

The curved surface of the cornea, and the lens

48
Q

What do you understand by the term ‘accommodation‘?

A

Accommodation is the way the eye can focus either near or distant objects to form a sharp image on the retina

49
Q

What part does the lens play in the the process of accommodation?

A

The lens is made thinner so that light from a distant object is refracted less, or fatter so that light from a close object is refracted more

50
Q

What happens to the ciliary muscle and lens for an eye to focus on a distant object?

A

The ciliary muscle relaxes and the lens gets thinner

51
Q

What happens to the ciliary muscle and lens for an eye to focus on a near object?

A

The ciliary muscle contracts and the lens gets thicker

52
Q

What is a cataract?

A

A cloudy patch on the lens

53
Q

Explain why cataracts cause blurred vision

A

Cataracts stop light from entering the eye as normal so less light reaches the retina

54
Q

What treatment is offered to people with cataracts?

A

The cataract lens can be surgically removed and is replaced by an artificial lens. Only one eye is done at a time so that the person can have vision

55
Q

What kind of eye defect can give rise to short-sightedness?

A

Long eyeballs, large eyeballs, too powerful a lens, or a combination of these defects

56
Q

What are the three names for the lenses that correct long-sightedness?

A
  • converging (oval)
  • convex (oval)
  • meniscus (convex one side, concave the other side)
57
Q

Name the nerve fibres which carry impulses from the sense organs to the central nervous system

A

Sensory

58
Q

How can we tell which part of the body a sensory nerve impulse comes from?

A

Each part of the body is connected to its own region of the brain

59
Q

What is the function of an axon?

A

To carry the nerve impulse away from the cell body

60
Q

Describe the transmission of information from the stimulus of rods and cones in a dog‘s eye when it sees a cat, to the dog‘s muscles (via the CNS) as it responds and runs after the cat

A

Rods and cones (stimulus) —> sensory neurone/ optic nerve —> CNS (relay neurone) —> motor neurone —> muscle cells (response)

61
Q

What is a reflex?

A

A fast, automatic response to a stimulus (does not involve brain)

62
Q

Explain why neurones can deliver information very quickly

A

The signal is transmitted by electrical impulses

63
Q

Explain why doctors use electrical impulses to stimulate different parts of the brain

A

To find out what different parts of the brain do

64
Q

How do nerve impulses travel from one nerve to another?

A

The neurotransmitter is released by the axon of one neurone and diffuses across the gap to the dendrite of the other neurone. The neurotransmitter is absorbed into the dendrite which sets off an electrical impulse down the neurone.