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A Level Biology OCR > Chapter 6- Cell Division > Flashcards

Chapter 6- Cell Division Flashcards

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1
Q

Name all the stages of Mitosis in order:

A
  1. Interphase
  2. Prophase
  3. Metaphase
  4. Anap.hase
  5. Telephase (cytokinesis)

just remember- IPMAT

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2
Q

What occurs during the Interphase part of Mitosis?

A
  1. DNA molecules of chromosomes replicating
  2. chromosomes dispersed in nucleus as chromatin.
  3. 46 x 2 = 96
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3
Q

What occurs during the Prophase part of Mitosis?

A
  1. Chromatin condenses into chromosomes
  2. = short + fat, so now visible
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4
Q

What occurs during the Metaphase part of Mitosis?

A
  1. Chromosomes line up on equator of cell
  2. Centromeres attach to spindle fibres
    (3. Longitudinal separation of chromatids (now chromosomes) occurs.)
  3. Chromatids remain joined at centromere.
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5
Q

What occurs during the Anaphase part of Mitosis?

A
  1. Centromeres divide
  2. Each set of chromosomes moves towards the opposite end of cell.
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6
Q

What occurs during the Telephase part of Mitosis?

A
  1. Spindle fibres disappear
  2. Chromosomes become diffused
  3. nuclear membrane + nucleolus reappear
  4. cytokinesis (cytoplasm division) occurs.
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7
Q

Define the term: Mitosis.

A

Mitosis- division into 2 genetically identical daughter cells, which are also genetically identical to parent cell.

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8
Q

Define the term: Meiosis.

A

Meiosis- division into 4 genetically unique daughter cells with half the chromosomes of parent cell (haploid).

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9
Q

Name the parts of the cell cycle in order:

A
  1. g1
  2. (g0)
  3. S
  4. g2
  5. Mitosis
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10
Q

What occurs during g1?

A

g1:
Period of cell growth before DNA is duplicated.
Interphase begins in daughter cells.
g0 also part of g1.
(semi conservative replication occurs in g1)

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11
Q

What occurs during g0?

A

g0:
cell cycle arrest: cell leaves cell cycle either temporarily or permanently.
1. DNA is damaged
2. Differentiation: cell becomes specialised to carry out a function- no longer divide after.
3. g0 phase maintains certain no. cells in specific tissue.

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12
Q

What occurs during S-phase?

A

S:
period when DNA is duplicated (chromosomes are duplicated).
the cell synthesises a complete copy of the DNA in its nucleus.

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13
Q

What occurs during g2?

A

g2:
period after DNA is duplicated.
cell prepares for division.
(interphase ends in parent cell.)

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14
Q

What occurs during M (mitosis) phase?

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telephase
  5. Cytokinesis.
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15
Q

What are Telomeres and what is Telomere Erosion?.

A

Human telomeres contain thousands of repeat of the nucleotide sequence TTAGGG. They are sequences found at the end of the chromosome.
DNA misses last bit every time it replicates.
Chromosomes are shortened after each replication.
Until they reach a point where they lose important genetic information.
The most common cause of ceased cell division

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16
Q

What is the name given to cells that have permanently halted growth?

A

Cellular Senescence.
Process in which cell growth and development is irreversibly halted.
Natural process of ‘ageing’.
More cells become senescent as we grow older.
Senescent cells remain metabolically active.

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17
Q

How does cell cycle control work?

A

Cells only divide when they are of appropriate size + replicated error-free.
DNA + chromosomes correctly positioned for mitosis.
Control mechanisms called ‘checkpoints’ are used by cell to ensure this.

18
Q

What is different about cancer cells and normal cells?

A

Cancer cells- cell division is uncontrolled.
Mass replication of cells that aren’t ‘self’.
Overides cell cycle, not checked, replicated quickly.

19
Q

What is Meiosis I ?

A

Meiosis I:
first division, 2 haploid cells created.
Reduction division.
Crossing Over occurs

20
Q

What is Meiosis II ?

A

Meiosis II:
second division, 4 haploid daughter cells created.

21
Q

How are gametes produced?

A

Through meiosis.

22
Q

What kind of cells are gamtes?

A

haploid cells- half the normal number of chromosomes. .

23
Q

What is a homologous chromosomes?

A

each pair contains one chromosomes from each parent, same genes but different alleles.
A homologous chromosome pertains to one of a pair of chromosomes with the same gene sequence.
A homologous pair consists of one paternal and one maternal chromosome. In humans, there are a total of 46 chromosomes in the nucleus of a somatic cell.

24
Q

What kind of cell is a somatic cell?

A

diploid cell.

25
Q

What is a zygote and how is it formed?

A

Zygote- fertilised egg cell.
Formed when 2 haploid gametes fuse.
THESE Gametes are genetically unique as they were formed by meiosis. (not mitosis!! before fertilisation, then mitosis. )

26
Q

What are homologous chromosomes?

A

chromosome pairs, 1 maternal and 1 paternal.
Position of genes on each homologous chromosome is same, however genes contain different alleles.

27
Q

What is a chromatin?

A

mass of genetic material composed of DNA + proteins that condense to form chromosomes during eukaryotic cell div.

28
Q

What is a chromatid?

A

is 1/2 of 2 identical copies of replicated chromosomes.

29
Q

What is a centromere?

A

During cell div, identical copies are joined together at region called centromere.

30
Q

What is a bivalent?

A

Bivalent- association of pair of homologous chromosomes physically held together by at least 1 DNA crossover.

31
Q

What occurs during Meiosis I: PMAT1

A
32
Q

What occurs during Meiosis II: PMAT2

A
33
Q

Describe how fungi reproduce:

A
34
Q

What is potency?

A

Potency = stem cell’s ability to divide.

35
Q

What does ‘Totipotent’ mean?

A

Totipotent:

cells can differentiate into any cell type. Includes zygote + first 16 cells of developing embryo.

36
Q

What does Pluripotent mean?

A

Pluripotent: cells can form any tissue type but not whole organism - present in early embryo.

37
Q

What does Multipotent mean?

A

Multipotent- cells are present in adults + form range of cells within certain tissue.

38
Q

Define differentiation:

A

Differentiation: in multicellular organisms diff. cells specialise, take on diff. roles in tissues + organs.

Involves expression of some genes in cell.

Undifferentiated cells can divide continually, whereas differentiated lose this ability.

39
Q

Describe two sources of animal stem cells, and what kind of stem cell they are?

A
40
Q

What is a source of plant stem cells and where are they found?

A

Plant Stem cells found in meristemic tissue- typically tip of root and shoot.

A Level Biology OCR (23 decks)

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