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Biology > Cell division and stem cells > Flashcards

Cell division and stem cells Flashcards

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1
Q

interphase

A
  • cell is said to be ‘at rest’
  • split into: first growth phase, synthesis phase (where DNA is replicated), second growth phase
  • DNA replicated and checked for errors
  • protein synthesis
  • mitochondria and chloroplasts grow and divide
  • normal metabolic functions
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2
Q

what is G0?

A
  • stage where cell moves out of cell cycle
  • permanent or temporary
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3
Q

reasons for g0

A
  • differentiation - cell becomes specialised to carry out a particular function - unable to divide
  • DNA has become damaged - enters permanent cell arrest - most cells do this as they can only divide a set no. of times
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4
Q

checkpoints of cell cycle

A

G1 - end of G1 phase before S phase
G2 - end of G2 phase, before mitotic phase
Spindle assembly - metaphase checkpoint during mitosis

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5
Q

G1 checkpoint

A
  • checks for cell size, DNA damage, growth factors, nutrients
  • if it passes checks, it is triggered for DNA replication
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6
Q

G2 checkpoint

A
  • checks for DNA damage and replication, cell size
  • checks if DNA replicated without error
  • if it passes checks it moves into mitosis
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7
Q

spindle assembly checkpoint/ metaphase checkpoint

A
  • checks all chromosomes attached to spindles and aligned
  • mitosis won’t happen if checkpoint not passed
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8
Q

mitosis definition

A
  • process of nuclear division before a cell physically divides in 2
  • DNA is copied into each of 2 daughter cells
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9
Q

why is mitosis needed?

A
  • it’s how organisms grow
  • basis of asexual reproduction
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10
Q

early prophase

A
  • chromosomes become more distinct - coil up, shorten, thicken
  • centriole divides
  • nucleolus less prominent
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11
Q

late prophase

A
  • chromosomes seen to consist of 2 chromatids joined by centromere
  • centrioles migrate to opposite poles
  • nucleolus continues to shrink and disappears
  • nuclear envelope disintegrates
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12
Q

metaphase

A
  • each centriole is at a pole
  • centrioles produce spindle fibres
  • spindle fibres attach to centromere of chromosomes
  • chromosomes pulled to equator
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13
Q

anaphase

A
  • spindle fibres contract
  • centromere divides and chromatids pulled to opposite poles of cell by centromere
  • each half recieves 1 chromatide from each chromosome
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14
Q

telophase

A
  • chromatids reach poles of spindle and begin to uncoil and become less distinct
  • nuclear envelope starts to reform
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15
Q

cytokinesis in animal cells

A
  • the cell divides by starting with constriction from edges of cell
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16
Q

cytokinesis in plant cells

A
  • cell wall is laid down
  • cell divides and daughter cells have same no. chromosomes and genetic makeup as each other and parent cell
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17
Q

how many chromosomes does a human body cell contain

A

46 chromosomes
23 pairs of homologous chromosomes

18
Q

are gametes haploid or diploid?

A

haploid - one copy of each chromosome

19
Q

homologous chromosome

A

same genes and alleles of that gene appear at same position on chromosome

20
Q

how is a zygote formed?

A

2 haploid cells fuse

21
Q

prophase I meiosis

A
  • chromosomes condense
  • nuclear envelope disintegrates
  • spindle fibres begin to form
  • homologous chromosomes pair up forming bivalents
  • crossing over occurs
22
Q

metaphase I meiosis

A
  • chromosomes line up on equator
  • spindle fibres attach to centromere
  • independent assortment - maternal and paternal chromosomes randomly put on either side of equator
23
Q

anaphase I

A
  • homologous chromosomes pulled by spindle fibres to poles - not pulled apart
  • causes variation
24
Q

telophase I meiosis

A
  • nuclear envelopes reform
  • chromosomes uncoil
  • cells undergo cytokinesis
  • cells now haploid
25
Q

prophase II meiosis

A

beginning of second division
- chromosomes recondense
- nuclear envelope breaks down again
- spindle fibres reform

26
Q

metaphase II meiosis

A
  • chromosomes lined on equator by spindle fibres
  • independent assortment again
  • more genetic variation
27
Q

ananphase II meisosis

A
  • chromatids split apart by sindle fibres
  • chromatids move to poles of cells
28
Q

telophase II meiosis

A
  • chromatids uncoil
  • nuclear envelopes reform
  • cytokinesis
  • 4 haploid daughter cells
29
Q

tissues definition and examples

A

collection of differentiated similar cells with specialist function
- animal tissues - nervous, epithelial, muscle, connective
- plant tissues - epidermis, vascular

30
Q

organ definition and examples

A

collection of tissues adapted to carry out particular function eg. heart, lungs, leaf

31
Q

organ system

A

multicellular organisms have interconnected organ systems
- each system has a number of organs to carry out functions
eg. digestive system, cardiovascular

32
Q

specialised cell

A

differentiated cells that carry out a particular function

33
Q

stem cells

A
  • undifferentiated cells originated from mitosis or meiosis
  • not adapted to particular function
  • unspecialised and have ability to differentiate and become any cell type
34
Q

totipotent

A
  • stem cells that can differentiate into any type of cell
  • eventually produce whole organism
  • eg. fertilised egg
35
Q

pluripotent

A
  • form all tissue types but not whole organisms
  • present in early embryos
  • origin of all different tissue types
36
Q

multipotent

A
  • can only form a range of cells within certain tissue type
  • eg. haematopetic stem cells in bone marrow - form types of blood cell
37
Q

how have stem cells in bone marrow adapted to erythrocytes function?

A
  • only few organelles - more room for haemoglobin
  • life span of 120 days - replaced constantly - stemm cell colonies in bone marrow produce 3 billion erythrocytes per kg of body mass per day
38
Q

how have stem cells in bone marrow adapted to neutrophils function?

A
  • live for about 6 hours - colonies of stem cells in bone marrow produce 1.6 billion per kg per hour
39
Q

embryonic stem cells

A
  • present at early stages of embyonic development - totipotent - after 7 days a blastocyst (mass of cells) forms and they are pluripotent until birth
40
Q

adult stem cells

A
  • bone marrow - multipotent
  • umbilical cord of newborn babies
41
Q

sources of plant stem cells

A

(pluripotent)
- meristems - found wherever growth is occurring eg. tip of roots and shoots
- between phloem and xylem - vascular cambium (can only differentiate into cells present in xylem and phloem)

42
Q

uses of stem cells

A
  • heart disease - muscle tissue damaged as result of heart attack
  • type 1 diabetes - insulin producing cells destroyed by body
  • Parkinson’s - shaking and rigidity caused by death of dopamine-producing cells in brain

Biology (17 decks)

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