2.1.6 Cell division, cell diversity and cellular organisation Flashcards

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1
Q

What happens during stage G1 of interphase?

(Growth stage 1)

A
  • Cellular contents (mitochondria, chloroplasts) are duplicated
  • Cell increases in size
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2
Q

What happens during stage S of interphase?

(Synthesis stage)

A

Chromosomes are duplicated in nucleus

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3
Q

What happens during stage G2 of interphase?

(Growth stage 2)

A
  • Cell continues to increase in size
  • Energy stores increased
  • Chromosomes checked for repairs
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4
Q

What happens during stage G0 of interphase?

(Resting state)

A

Cell leaves cycle temporarily or permanently

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5
Q

Why does cell enter stage G0 of interphase?

A
  • Differentitation
  • Damage to DNA
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6
Q

What are checkpoints in interphase?

A

Requirements that have to be fulfilled before the next stage can begin

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7
Q

What is checked for in the checkpoints of interphase?

A
  • Cell size
  • DNA damage
  • DNA replication without error
  • Nutrient availablity
  • Chromosome attachment to spindle
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8
Q

What are the three checkpoints of interphase?

A
  • G1 checkpoint
  • G2 checkpoint
  • Spindle assembly checkpoint
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9
Q

How many daughter cells are produced from mitosis?

A

Two genetically identical diploid cells

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10
Q

How many daughter cells are produced from meiosis?

A

Four genetically different haploid cells

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11
Q

What is mitosis important for?

A
  • Growth and repair
  • Asexual reproduction
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12
Q

In terms of n what are the changes in chromosome number before, during and after for mitosis?

A

2n -> 4n -> 2n

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13
Q

What type of division is meiosis known as?

A

Reduction division

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14
Q

What are homologous chromosomes?

A

Matching sets of chromosomes where each one has the same genes at the same position (loci)

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15
Q

What are alleles?

A

Different versions of the same gene (located in the same positions)

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16
Q

What happens during meiosis I?

A

Homologous chromosomes are separated into two different cells

17
Q

What happens during meiosis II?

A

Pairs of chromatids in each daughter cell are separated to form four cells in total (similar to mitosis)

18
Q

When does crossing over occur in meiosis?

A

Prophase 1

19
Q

What is crossing over?

A

Homologous chromosomes pair up and form bivalents (occurs when chromatids entangle)

20
Q

What is independent assortment?

A

Orientation of homologous pair at equator is random and independent so different combinations of alleles face the poles

21
Q

When does independent assortment occur in meiosis?

A

Metaphase 1 and metaphase 2

22
Q

What results in genetic variation in meiosis?

A

Crossing over and independent assortment

23
Q

What is an organ?

A

Collection of tissues adapted to perform a particular function

24
Q

What is an organ system?

A

Composed of several organs working together to carry out a major function e.g. cardiovascular system

25
Q

What are stem cells?

A

Undifferentiated cells with the potential to differentiate into any specialised cell

26
Q

What are totipotent stem cells?

A
  • Can differentiate into ANY type of cell
  • Can produce a whole organism
  • E.g. zygote
27
Q

What are pluripotent stem cells?

A
  • Can form all tissue types
  • BUT NOT whole organisms
  • Present in early embryos
28
Q

What are multipotent stem cells?

A
  • Can only form a range of cells within a certain type of tissue tissue
  • E.g. stem cells in bone marrow can form different blood cells
29
Q

Why do erythrocytes and neutrophils need to be constantly replaced?

A

They have short life spans (red blood cell has no nucleus so cannot multiply)

30
Q

What are the sources of animal stem cells?

A
  • Embryonic stem cells (totipotent)
  • Tissue stem cells: bone marrow and umbilical cord (both multipotent)
31
Q

When do embryonic stem cells enter the pluripotent stage?

A

After seven days, when mass of cells (blastocyst) has formed

32
Q

What is the source of stem cells in plants?

A

Meristematic tissue (pluripotent)
- Found in the apical meristems (tips of shoots and roots)
- Found in the vascular cambium (these differentiate into cells needed in xylem and phloem)

33
Q

What are the uses of stem cells?

A
  • Repairing damaged tissue
  • Treating neurological conditions e.g. Alzheimerโ€™s and Parkinsonโ€™s
34
Q

In terms of n what are the changes in chromosome number before, during and after for meiosis?

A

2n -> 4n -> 2n -> n