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Biology B4, B5, B6 > B5 - Growth and development > Flashcards

B5 - Growth and development Flashcards

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1
Q

In organisms that are MULTICELLULAR, cells are ______ to do different jobs.

A

In organisms that are MULTICELLULAR, cells are SPECIALISED to do different jobs.

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2
Q

Cells of the same type are grouped into _____.

A

Cells of the same type are grouped into TISSUES.

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3
Q

Different tissues are grouped together, and work together, in _____.

A

Different tissues are grouped together, and work together, in ORGANS.

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4
Q

Organs work together as __________.

A

Organs work together as body systems.

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5
Q

How does a fertilised egg cell (zygote) divide to form an embryo?

A

Using MITOSIS

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6
Q

In a human embryo up to (and including) the eight cell stage, what are all the cells classified as?

A

IDENTICAL - EMBRYONIC STEM CELLS.

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7
Q

What can embryonic stem cells do?

A

They are UNSPECIALISED and TOTIPOTENT. They can produce any cell type in the body.

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8
Q

After the eight cell stage, what happens to most of the embryo cells?

A

They become SPECIALISED (DIFFERENTIATION) and different tissues form.

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9
Q

What happens to some cells (adult stem cells)?

A

They can remain UNSPECIALISED and can become specialised at a later stage to become many, but not all, types of cell required by the organism. e.g. bone marrow

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10
Q

In plants, what is the special region called where it contains cells that are mitotically active?

A

MERISTEMS (the tip of the root)

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11
Q

The new cells produced from plant meristems are classified as what?

A

UNSPECIALISED and can develop into any kind of PLANT CELLS

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12
Q

Unspecialised plant cells can become….?

A

SPECIALISED

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13
Q

What can specialised plant cells form into?

A

Different types of tissue (XYLEM and PHLOEM) within organs (flowers, leave, stems and roots).

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14
Q

What is the function of the tissue ‘XYLEM’?

A

Transports water and mineral salts

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15
Q

What is the function of the TISSUE ‘PHLOEM’?

A

Transports the products of photosynthesis

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16
Q

When meristem cells divide into two, what happens to the new cell that is produced?

A

The new cell produced can differentiate into different cell types (the other stays as a meristematic cell).

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17
Q

In plants, the only cells that divide are in _________.

A

meristems

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18
Q

Other than cells, what can meristems produce?

A

GROWTH in HEIGHT and WIDTH (by division of meristem cells, followed by enlargement on one of the daughter cells).

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19
Q

What can the presence of meristems (as sources of unspecialised cells) allow?

A

The production of clones of a plant from cuttings.

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20
Q

What are plant cuttings?

A

Pieces of plants, e.g. plant stems, that have meristems.

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21
Q

Why are plant cuttings used?

A
  1. To reproduce a plant with DESIRABLE features.

2. Produce clones that are genetically identical to the parent plant.

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22
Q

How is root growth in cuttings promoted?

A

By PLANT HORMONES (using hormone rooting powder)>

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23
Q

What is another method of cloning other than using plant cuttings?

A

TISSUE CULTURE

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24
Q

What is Tissue Culture?

A

A small piece of tissue, or a few cells are placed on agar jelly containing nutrients and plant hormones. Each will grow into a small plant or plantlet.

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25
Q

What is one plant hormone that is included in the agar for tissue culture and in hormone rooting powder?

A

AUXINS

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26
Q

What do AUXINS contribute to?

A

The increases of cell division and cell enlargement, promoting the growth of the plant tissue.

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27
Q

What factor affects the plant growth and development?

A

The ENVIRONMENT

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28
Q

What is PHOTOTROPISM?

A

The plant’s response to the direction of light

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29
Q

Because shoots (the upper part of the plant) grow TOWARDS the light, what are they known as?

A

POSITIVELY phototropic

30
Q

Because roots (the end of the plant) grow AWAY from the light, what are they known as?

A

NEGATIVELY phototropic

31
Q

In what way does POSITIVE PHOTOTROPISM increase the plant’s chance of survival?

A

Plants need sunlight for photosynthesis in order to gain energy and grow. Photosynthesis occurs mainly in the leaves, so it’s important for plant shoots, which will grow leaves, to grow TOWARDS light.

32
Q

In what way does NEGATIVE PHOTOTROPISM increase the plant’s chance of survival?

A

Plants need nutrients and water from the soil to grow. Phototropism means roots grow AWAY from light, down into the soil where they can absorb the water and nutrients the plant needs for healthy growth.

33
Q

What are AUXINS?

A

Chemicals/plant growth hormones that CONTROL GROWTH near the tips of shoots and roots.

34
Q

Where are auxins produced?

A

in the TIPS

35
Q

How do auxins stimulate the cell elongation (enlargement) process, which occurs just behind the tips?

A

The auxins DIFFUSES BACKWARDS

36
Q

If the tip of a shoot is removed, what happens?

A

No auxins are available and the shoot may stop growing.

37
Q

What are the 3 responses that auxins are involved in?

A

LIGHT, GRAVITY, WATER

38
Q

How do auxins make shoots grow towards the light?

A

When a shoot tip is exposed to light, more auxins accumulate/distribute on the side that’s in the shade than the side that’s in the light.
This makes the cells grow (elongate) faster on the shaded side, so the shoot grow TOWARDS the light.

39
Q

What is Mitosis?

A

A type of cell division that takes place when an organism grows, and cells divide to repair tissues?

40
Q

What does the result of Mitosis produce?

A

TWO new DAUGHTER CELLS that are genetically identical (i.e. have the same number of chromosomes) as the parent cell.

41
Q

What are the 2 stages of the process of the CELL CYCLE?

A
  1. The number of organelles increases during cell growth.

2. The chromosomes are copied when the two strands of each DNA molecule separate and new strands form alongside them.

42
Q

What are the stages of Mitosis?

A
  1. Each chromosome makes an identical copy of itself.
  2. Chromosomes line up along the centre of the cell.
  3. Four chromosomes go into each daughter cell
  4. Four chromosomes go into each daughter cell. The cells divide into two. Each daughter cell is an exact copy of the original cell.
43
Q

What is Meiosis?

A

A type of cell division that produces GAMETES (sex cells - eggs and sperm in animals; eggs and pollen grains in flowering plants)

44
Q

In humans, how many chromosomes do gametes contain?

A

23 - HALF the number of chromosome as body cells.

i.e. one chromosome from each pair.

45
Q

At fertilisation, what happens in terms of gametes?

A

The gametes (sperm and egg) join together to form a zygote with 46 chromosome.

46
Q

Why is it important that gametes contain 23 chromosomes?

A

Because, otherwise, the zygote would end up with 92 chromosomes.

47
Q

What does the zygote contain?

A

A set of chromosomes from each parent.

48
Q

What are the stages of Meiosis?

A
  1. The chromosomes are copied (of the parent cell which contains two pairs of chromosomes) and pair up.
  2. The cell divides into two.
  3. And divides in two again.
  4. This produces four gametes (eggs or sperms), each with half the number of chromosomes.
49
Q

What are 3 features of chromosomes?

A
  1. Thread-like structures found in the nucleus
  2. Are made from a DNA molecule
  3. Can be grouped into pairs (humans have 23 pairs).
50
Q

What is the scientific name for the structure of DNA?

A

DOUBLE HELIX

51
Q

What are the 3 units that make up DNA?

A
  1. PHOSPHATE
  2. SUGAR
  3. BASE
52
Q

What does a DNA Molecule consist of?

A

2 Strands coiled together, facing each other.

53
Q

What are the 4 bases? What are the pairs?

A

A (Adenine), C (Cytosine), T (Thymine), G (Guanine).
A pairs with T
C with G

54
Q

What does the order of the bases in a gene make up?

A

The GENETIC CODE

55
Q

What does the Genetic Code present?

A

It gives instructions for the assembly of a protein (the AMINO ACIDS that are in the protein, and the order in which they’re arranged.)

56
Q

What particular set of bases codes for one amino acid?

A

Each set of THREE bases (triplet) codes for one amino acid.

57
Q

In plant and animal cells, where is the genetic code that carry the INSTRUCTIONS for protein synthesis located?

A

On the DNA in the CELL NUCLEUS

58
Q

Where is protein SYNTHESIS located in plant and animal cells?

A

In the CYTOPLASM

59
Q

How is the genetic code transmitted to the cytoplasm in order for protein synthesis to activate?

A

Genes do NOT leave the nucleus so a copy of the gene (Messenger RNA = mRNA) is produced to CARRY the genetic code to the cytoplasm, using the DNA as a template.

60
Q

What is the full process/stages of the transport of genetic code to the cytoplasm?

A
  1. The two DNA strands UNZIP.
  2. A molecule (mRNA) is made using ONE STRAND of the DNA as a template.
  3. The mRNA molecule moves OUT of the nucleus and joins with a ribosome in the cytoplasm.
  4. The job of the ribosome is to stick amino acids together in a chain to make a protein, following the order of bases in the messenger RNA. This is supported by Transfer RNAs (tRNA).
  5. The protein chain leaves the ribosome.
61
Q

What is important to know about cells in terms of the genes it has?

A

ALL body cells in an organism contain the SAME genes but many genes in a particular cell are not active (SWITCHED OFF) because the cell only produces the SPECIFIC PROTEINS it needs.

62
Q

What is the difference between specialised and embryonic stem cells in terms of switching genes on and off?

A

Specialised - they make specific proteins and only the genes needed for the cell are switched on.

Embryonic stem cells - ANY gene can be switched on during development to produce any type of specialised cell.

63
Q

What do Embryonic Stem Cells (and adult stem cells) have the potential to do?

A

To replace cells needed to replace damaged tissues

64
Q

Where are adult stem cells found in the body?

A

Various locations, e.g. the bone marrow

65
Q

Why does the use of embryonic stem cells raise ethical issues?

A

Because in removing cells, the embryo is destroyed.

66
Q

How are embryonic stem cells usually removed?

A

From surplus embryos from in-vitro fertilisation (IVF).

67
Q

How would the abuse of embryonic stem cells be even more controversial?

A

The CREATION of embryos produced with the INTENTION of destroying them?

68
Q

Work with stem cells is the subject of….?

A

Government regulation

69
Q

What type of cloning overcomes some ethical issues of using embryonic stem cells? What does it involve?

A

THERAPEUTIC CLONING. It involves replacing the nucleus of an egg by the nucleus of a body cell and stimulating the egg cell to divide to produce an ‘embryo’.

70
Q

What does therapeutic cloning NOT require?

A

Fertilisation - and the cells will be genetically identical to the patient’s. The ‘embryo’ produced is still destroyed after stem cells are extracted.

71
Q

Using chemical treatments, what have scientists managed to do? What does this technique enable? What is the hope of this technique?

A

To transform mammalian body cells into stem cells.
This enables inactive genes in the nuclei of body cells to be reactivated. The hope is that the transformed cells will be able to form cells of ALL cell types.

Biology B4, B5, B6 (3 decks)

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