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Ag Science > Chapter 15 -Cell Division > Flashcards

Chapter 15 -Cell Division Flashcards

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1
Q

What appears as a dark mass when viewing cells under a light microscope? And what does this dark mass contain?

A

The nucleus of the cell appears as a dark mass, and it is composed of a material known as chromatin.

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2
Q

What is chromatin?

A

Chromatin is a mixture of DNA and Protein.

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3
Q

What happens when the cell is about to divide?

A

The chromatin (the mixture of DNA and protein and is also found in the nucleus of a cell) forms structures called chromosomes.

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4
Q

What are chromosomes?

A

Chromosomes are composed of DNA and Protein and are visible only during cell devision.

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5
Q

What is a gene?

A

A gene is a part of a chromosome that contains information to produce a protein.

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6
Q

Do chromosomes contain thousands of genes?

A

Yes, chromosomes contain thousands of genes.

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7
Q

What do genes determine?

A

Genes determine the sequence of amino acids required to produce many different types of proteins.

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8
Q

What functions do the proteins have?

A

Structural proteins (keratin), hormones (insulin), antibodies, enzymes (amylase) and transport proteins (haemoglobin in red blood cells)

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9
Q

What is a sequence?

A

The order in which genes are arranged on a chromosome.

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10
Q

What are Honologous chromosomes?

A

A pair of chromosomes of the same size that have the same gene sequence.

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11
Q

What is a diploid? And what is it also known as?

A

A cell is diploid or 2n when it has a full set of chromosomes. ( a cell with a complete set of chromosomes ).

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12
Q

How many chromosomes do humans have? Say how many pairs this number translates to also.

A

A human has 46 chromosomes (23 pairs) in their body cells.

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13
Q

What is the chromosome number for cattle?

A

60

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14
Q

What is the chromosome number for sheep?

A

54

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15
Q

What is the chromosome number for pig?

A

38

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16
Q

What is the chromosome number for chicken?

A

78

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17
Q

Cell division must occur. WHY?

A

Cell division must occur in order for animals and plants to grow, to repair and replace dead and worn-out cells and to reproduce.

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18
Q

What are the two types of cell division?

A

Mitosis and Meiosis

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19
Q

Where does mitosis occur?

A

Mitosis occurs in normal body cells (referred to as somatic cells)

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20
Q

Where does meiosis occur?

A

Meiosis occurs in the testes and ovaries to produce gametes.

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21
Q

What are somatic cells?

A

Somatic cells are all the body cells of an organism, apart from the sperm and egg cells. Somatic cells contain a full set of chromosomes.

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22
Q

What phase occurs before cell divison commences? And what is this known as?

A

The cell prepares itself for mitosis by gradually getting bigger and producing additional cell organelles such as mitochondria. This phase is called interphase.

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23
Q

Do normal somatic cells spend the majority of the cell cycle in this phase?

A

Yes, normal somatic cells spend the majority of the cell cycle in interphase.

24
Q

During interphase what is present and the chromatin has not yet formed what?

A

During interphase the nuclear membrane is present and the chromatin has not yet formed chromosomes.

25
Q

When a cell is in interphase is it dividing or not?

A

When a cell is in interphase it has not yet begun dividing.

26
Q

What iss the Cell Cycle?

A

The cycle of growth and division of a eukaryotic cell.

27
Q

Once cell division commences, what 4 stages cna it be divided into?

A

Prophase, Metaphase, Anaphase and Telophase.

28
Q

What is the first stage of Mitosis?

A

Prophase is the first stage of mitosis.

29
Q

What happens to the chromosomes during Prophase?

A

The chromosomes become visible in the cell. Each chromosome duplicates itself, so that the chromosomes appear as two strands (called sister chromatids) joined in the centre by the centromere. The old chromosome is attached to an identical copy of itself.

30
Q

Explain what happens during the first stage of mitosis.

A
  • Chromosomes become visible and duplicate themselves (known as sister chromatids)
  • The nuclear membrane and other cell organelles dissapear.
  • Spindle Fivres start to form.
31
Q

Explain what happens during Metaphase.

A
  • The chromosomes line up in the centre of the cell.

- The spindle fibres attach themselves to the centrometre of the chromosome.

32
Q

Explain what happens during Anaphase.

A
  • The spindle fibres contract, separating the duplicated chromosome from its copy.
  • The chromosomes are pulled to opposite poles of the cell.
33
Q

Explain what happens during Telophase.

A
  • This is the final stage of mitosis.
  • The chromosomes begin to uncoil to form chromatin
  • The spindle fibres break down.
  • The nuclear membrane reforms.
  • At the end of telephase, the cytoplasm divides to form 2 cells.
  • Division of the cytoplasm is known as cytokinesis.
34
Q

What is the division of the cytoplasm known as and what stage of mitosis does in occur in?

A

The division of the cytoplasm is known as cytokinesis and it occurs in the telophase stage, the last stage of mitosis.

35
Q

Explain Telophase in plant cells.

A

In plant cells, a cell plate grows between the two new cells and from this a new cell wall develops, thus separating the two cells.

36
Q

Where does mitosis occur in plants?

A

Mitosis occurs in meristematic tissue in the tips of plant roots and shoots, and cambium tissue, between the phloem and xylem in vascular bundles, of dicot stems, is also meristematic tissue.

37
Q

Where does mitosis occur in animals?

A

Mitosis occurs in the bone marrow to produce red blood cells, the cells lining the digestive tract and skin cells.

38
Q

Where does mitosis occur very rapidly in animals?

A

Mitosis occurs very rapidly in tbe development of a zygote into an embryo in animals.

39
Q

Where does mitosis occur in insects?

A

Mitosis occurs during metamorphosis in insects.

40
Q

Give 4 points of the significance of mitosis.

A
  • Mitosis produces two identical daughter cells that have the same number of chromosomes (sister chromatids)
  • Genetic information on the chromosomes is identical
  • Mitosis is important for growth and repair of dead and worn out cells.
  • Some organisms can reproduce asexually by mitosis, e,g. Yeast cells reproduce by budding.
41
Q

What are sisyer chromatids joined by in the centre?

A

Sister chromatids are joined in the centre by the centromere.

42
Q

What location does mitosis continuously occur in, in plants?

A

Mitosis continuously occurs in the tips of shoots and root in plants.

43
Q

What is mertistematic tissue constantly producing in the locations of mitosis in plants?

A

Meristematic tissue in these locations (tips of roots and shoots) is constantly producing new cells by mitosis to allow for plant growth.

44
Q

What is also meristematic tissue, and where is it located?

A

Cambium tissue is also maristematic tissue and it is located in between the phloem and xylem in vascular bundles of dicot stems.

45
Q

Where is mitosis continuously occuring in animals? and why?

A

Mitosis is continuously occuring in the bone marrow of animals to produce new red blood cells, the cells linig tbe digestive tract and skin cells.

46
Q

What does mitosis also occur in animals?

A

Mitosis occurs very rapidly in the development of a zygote into an embryo in animals.

47
Q

What does mitosis occur in insects

A

Mitosis occurs during metamorphosis in insects.

48
Q

What is meiosis also known as? And why?

A

Meiosis is also known as reduction division because they only have half a set of chromosomes.

49
Q

Where does meiosis occur in animals and what does meiosis produce?

A

Meiosis occurs in the testes and ovaries of animals and produces four non identical cells that have half the number of chromosomes of the parent.

50
Q

What are the four non identical cells that have half the number of chromosomes of the parent, and are produced by meiois, called?

A

The four non identical cells that have half the number of chromosomes of the parent and are produced by meiosis are called gametes or sex cells (egg and sperm).

51
Q

What is a haploid? And what is it also known as? What are haploid?

A

A cell is haploid or n when it only has half a set of chromosomes. Gametes are haploid or n.

52
Q

What is crossing over? And what form of cell divison does crossing over only occur in? And what does crossing over result in?

A

Crossing over is the process where homologous chromosomes exchange genetic information. This process only occurs during meiosis and results in genetic variation in the offspring.

53
Q

Where does meiosis take place in plants? During what? And what other part of the plant does meiosis occur in? In order to produce what?

A

Meiosis takes place in the anther of plants during the production of pollen grains and also in the ovule in order to produce the egg cell and the two polar nuclei cells.

54
Q

What allows each gamete to have one chromosome from each pair?

A

Meiosis allows for each gamete to have one chromosome from each pair, for example, in humans, the gametes have 23 chromosomes.

55
Q

Is the diploid number of chromosomes restored in the zygote on fertilisation?

A

Yes, the diploid number of chromosomes is restored in the zygote on fertilisation.

56
Q

What would the offspring have compared to the parent if meiosis did not occur?

A

If meiosis did not occur, the offspring would have double the number of chromosomes the parent had.

57
Q

What are the 3 signicances of meiosis

A

The 3 significances of meiosis are-

  • Meiosis reduces the chromosome number in the cell by half
  • the chromosome diploid number is restored in the zygote on fertalisation.
  • crossing over during meiosis allows for genetic variation in the offspring as new gene combinations are produced.

Ag Science (10 decks)

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