Topic 2a - Cell Division and Stem Cells Flashcards

1
Q

What do you call body cells that have two copies of each cell?

A

Diploid cells

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2
Q

What is a chromosome?

A

Long lengths of a molecule called DNA. The DNA is coiled up to form the arms of the chromosome.

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3
Q

What is the cell cycle?

A

The cell cycle starts when a cell has been produced by cell division and ends with the cell dividing to produce two identical diploid cells.

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4
Q

What is the stage of the cell cycle where the cell divides, called?

A

Mitosis

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5
Q

What is mitosis?

A

Mitosis is when a cell reproduces itself by splitting in two to form two genetically identical offspring.
It usually refers to the division of the nucleus rather than the whole cell.

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6
Q

What happens during interphase, during the cell cycle?

A

1) In a cell that’s not dividing, the DNA is all spread out in long strings
2) Before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
3) It then duplicates its DNA- so there’s one copy of each chromosome for each new cell. The DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other. Each ‘arm’ is called a chromatid.

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7
Q

What happens during mitosis, during the cell cycle?

A

1) Prophase: the chromosomes condense, getting shorter and fatter. The membrane
around the nucleus breaks down and the chromosomes lie free in the cytoplasm.
2) Metaphase: the chromosomes line up at the centre of the cell.
3) Anaphase: spindle fibres pull the chromosomes apart. The two arms of each chromosome (chromatids) are pulled to opposite ends of the cell.
4) Telophase: membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells — the nucleus has been divided.
Before telophase ends, the cytoplasm and cell membrane divide to form two separate cells — this process is called cytokinesis.

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8
Q

What happens after mitosis, in the cell cycle?

A

At the end of mitosis, the cell has produced two new daughter cells. Each daughter cell contains exactly the same set of chromosomes in its nucleus - the two cells are genetically identical. They’re also genetically identical to the diploid parent cell. This makes the daughter cells diploid too.

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9
Q

What are the uses of mitosis?

A
  • By multicellular organisms to grow
  • By multicellular organisms to replace cells that have been damaged
  • By some organisms to reproduce by asexual reproduction
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10
Q

How do you calculate the number of cells there are after multiple division of cell by mitosis?

A

2^n (n = the number of divisions by mitosis)

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11
Q

To what processes do animal cells grow and develop?

A
  • Cell division: happens by mitosis
  • Cell differentiation: the process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently because different cell types can carry out different functions.
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12
Q

To what processes do plant cells grow and develop?

A
  • Cell division: happens by mitosis
  • Cell differentiation: the process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently because different cell types can carry out different functions.
  • Cell elongation: the plant cell expands, making the cell bigger, so making the plant grow
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13
Q

When do animal cells grow?

A

Animal cells tend to grow at a faster rate when they’re younger, than when they’re older

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14
Q

When do plant cells grow?

A

Cell division usually happens at the tips of roots and shoots (in areas called meristems). Plants grow continuously, at all ages.

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15
Q

What is the rate at which the cells divide by mitosis controlled by?

A

chemical genes in an organism’s DNA

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16
Q

What happens if there is a change in one of the genes that controls cell division?

A

The cells start dividing uncontrollably. This can result in a mass of abnormal cells called tumour. If the tumour invades and destroys surrounding tissues, it is called cancer.

17
Q

What is a percentile chart used for?

A

To assess a child’s growth over time, so an overall pattern can be developed, and any problems highlighted.

18
Q

What 3 results are plotted on a percentile chart?

A
  • Length of baby
  • Mass of baby
  • Head circumference of baby
19
Q

What do the percentiles show?

A

e.g., the 50th percentile shows the measurement (e.g., mass, head circumference or length) 50% of babies would have reached at that age

20
Q

What are stem cells?

A

Cells that are undifferentiated (they haven’t changed to become specialised for a particular function). They can divide to produce lots more undifferentiated cells. These new cells can then develop into different types of cell, depending on what instructions they’re given.

21
Q

Where are stem cells found?

A

Stem cells are found in early human embryos. These embryonic stem cells have the potential to divide and produce any kind of cell at all. The embryonic stem cells are really important for the growth and development of organisms, as all the cells in a human being have come from those few cells in the early embryo.

22
Q

What are adult stem cells used to do in medicine?

A

To cure disease, e.g., people with some blood diseases (e.g. sickle cell anaemia, a disease which affects the red blood cells) can be treated by bone marrow transplants. Bone marrow contains adult stem cells that can turn into new blood cells to replace the faulty old ones.

23
Q

What are embryonic stem cells in medicine used for?

A

Scientists have experimented with extracting stem cells from very early human embryos and growing them. Under certain conditions, the stem cells can be stimulated to differentiate into specialised cells. In the future, it might be possible to use embryonic stem cells to replace faulty cells in sick people.

24
Q

What are the issues involved in using stem cells?

A
  • Tumour development
  • Disease transmission
  • Rejection
25
Q

How is tumour development an issue involved in using stem cells?

A

Stem cells divide very quickly. If scientists are unable to control the rate at which the transplanted cells divide inside a patient, a tumour may develop.

26
Q

How is disease transmission an issue involved in using stem cells?

A

Viruses live inside cells. If donor stem cells are infected with a virus and this isn’t picked up, the virus could be passed on to the recipient and so make them sicker.

27
Q

How is rejection an issue involved in using stem cells?

A

If the transplanted cells aren’t grown using the patient’s own stem cells, the patient’s body may recognise the cells as foreign and trigger an immune response to try to get rid of them. The patient can take drugs to suppress this response, but this makes them susceptible to diseases.

28
Q

What are the ethical issues involved in using stem cells?

A

Some people are against it, because they feel that human embryos shouldn’t be used for experiments since each one is a potential human life, but the embryos used are unwanted ones from fertility clinics, so if they weren’t used for research, they’d probably just be destroyed.

29
Q

What are stem cells in plants like?

A

Meristems produce unspecialised cells that are able to divide and form any cell type in the plant — they act like embryonic stem cells. But unlike human stem cells, these cells can divide and differentiate to generate any type of cell for as long as the plant lives.
The unspecialised cells go on to form specialised tissues like xylem and phloem.