B2 Cell Divison Flashcards

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1
Q

What do chromosomes do?

A

Chromosomes carry genes that contain instructions for making new cells, organs, and tissues.

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2
Q

Define gene

A

A small packet of information that controls a characteristic (or part of it) of your body.

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3
Q

How many pairs of chromosomes do we have?

A

23 pairs = 46 chromosomes

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4
Q

Where are chromosomes found?

A

In the nucleus of cells

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5
Q

How many chromosomes do gametes have?

A

23 chromosomes (1 per pair)

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6
Q

Why is mitosis needed?

A

For growth and replacement of cells (e.g. at the site of a wound, during production of RBS in bone marrow, during growth spurts etc…)

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7
Q

How does the length of the cell cycle vary during: baby development (before birth), childhood, and after puberty?

A

Baby development before birth: Short
Childhood: Fairly rapid
After puberty: Slows down

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8
Q

Summarise the stages of the cell cycle (3 stages)

A

1) Cells grow bigger, increase mass to carry out normal cell activities. Cells replicate their DNA to form two copies of each chromosome. Cells increase the amount of sub-cellular structures (e.g mitochondria, ribosomes) {Longest Stage}.
2) Mitosis: One set of chromosomes is pulled to each end of the cell and the nucleus divides.
3) Cytoplasm and cell membrane divide to form two identical daughter cells.

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9
Q

Why is cell division by mitosis important?

A

It’s important in the growth and development of multicellular organisms.

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10
Q

Define DNA

A

A unique molecule which makes up our chromosomes

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11
Q

Define stem cells

A

An undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type.

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12
Q

What happens as an organism develops?

A

Cells differentiate to form different types

of cells.

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13
Q

When do animal cells become specialised?

A

In animals, most cells become specialised in early life.

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14
Q

What happens when a cell becomes specialised?

A

Some of its genes have been switched on; others have turned off. The cell acquires different sub-cellular structures to carry out specific functions.

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15
Q

Describe the restriction of cell division in mature animals

A

In mature animals, cell division is mainly restricted to repair and replacement.

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16
Q

How do specialised cells divide and what are the restrictions of specialised cells dividing?

A

Specialised cells can divide by mitosis; they can only form the same sort of cell (e.g muscle cells divide to form more muscle cells).

17
Q

List 2 examples of cells which can’t divide and describe how they are replaced

A

Red blood cells and skin cells can’t divide so they are replaced by adult stem cells.

18
Q

Can nerve cells divide? If not, how are they replaced?

A

Nerve cells can’t divide, once differentiated and they can’t be replaced by stem cells. Therefore, damaged nerve cells usually aren’t replaced.

19
Q

How does plant cell differentiation differ from animal cell differentiation?

A

Plant cells can differentiate throughout their lives.

20
Q

Where are undifferentiated cells formed (plants)?

A

At the meristems (active regions of stems and roots).

21
Q

What happens at the meristems?

A

Mitosis continuously happens at the meristems. The cells grow and elongate before they differentiate.

22
Q

Describe how plant cells can redifferentiate

A

Plant cells can move from one part of a plant to another, where it can redifferentiate and become a different cell.

23
Q

Explain how a piece of leaf tissue can produce identicall plant clones

A

1) In right conditions, a plant cell will become unspecialised and undergo mitosis many times.
2) Undifferentiated cells will produce more cells by mitosis.
3) These cells will then differentiate to form tissues.

24
Q

What does an egg and sperm cell form?

A

A zygote (single new cell)

25
Q

How is an embryo formed?

A

When the zygote divides and becomes a hollow ball of cells - the embryo

26
Q

Where are embryonic stem cells taken from?

A

The inner cells of the ball (embryo) are embryonic stem cells.

27
Q

Where, in the human body, is there a good source of adult stem cells?

A

Bone marrow

28
Q

List 2 conditions stem cells may be able tohelp

A

Paralysis and diabetes

29
Q

Stem cells from meristems can be used to make clones of mature parent plants quickly. List reasons this is helpful (5 reasons)

A
  • Can produce large numbers of plants reliably and safely.
  • Can save rare plants from extinction.
  • Produce large population of plants for scientific research.
  • Horticulture: produce large numbers of plants for sale.
  • Agriculture: produce large numbers of plants with special features (e.g disease resistance).
30
Q

How do embryonic stem cells differ from adult stem cells?

A

Embryonic stem cells can differentiate into any type of cell; adult stem cells can only differentiate into related types of cells.

31
Q

Cons of embryonic stem cells

A
  • Religious beliefs: can’t accept interference with human reproduction.
  • Progress in therapies involving embryonic stem cells has been slow, difficult, and expensive.
  • Difficult to persuade embryonic stem cells to differentiate into other types of cells.
  • Divide and grow rapidly: could potentially cause cancer.
32
Q

Cons of adult stem cells

A
  • May be infected with viruses which could transfer infections to the patient.
  • If used to treat an unrelated person, could trigger an immune response: patient would have to take immunosuppresant drugs to stop the body rejecting the cells.
  • A lot of money and time is being wasted on stem cell research.
33
Q

Pros of using stem cells

A
  • Scientists have found embryonic stem cells in the umbilical cord blood of babies and in the ammiotic fluid that surrounds the fetus: can overcome ethic problems.
  • Scientists are finding ways to grow adult stem cells, due to limited range: avoids ethic problems and have been used to treat forms of heart disease and grow organs such as tracheas.
34
Q

What is the area of stem cell research known as?

A

Therapeutic cloning

35
Q

What happens in therapeutic cloning?

A

An embryo is produced with the same genes as the patient so the stem cells produced are not rejected.