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Biology: Unit 2 > 2.6: Cell division > Flashcards

2.6: Cell division Flashcards

1
Q

How do eukaryotic cells, prokaryotic cells and viruses divide?

A
  • Eukaryotic cells enter the cell cycle and divide by mitosis or meiosis
  • Prokaryotic cells replicate by binary fission
  • Viruses do not undergo cell division as they are non living
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2
Q

What are the three stages of the cell cycle?

A
  1. Interphase
  2. Nuclear division (mitosis or meiosis)
  3. Cytokenisis
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3
Q

What is interphase?

A

The longest stage of the cell cycle.
Consists of G1, S and G2

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4
Q

What happens during G1?

A
  • Protein synthesis occurs to make proteins involved in synthesising organelles
  • The organelles replicate
  • Cell is checked that it is the correct size, has the correct nutrients, growth factors and that there is no damages DNA. if a cell doesn’t grow pass those checks replication will not continue
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5
Q

What happens during S phase?

A

DNA is replicated

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6
Q

What happens during G2?

A
  • Cell continues to grow
  • energy stores increase
  • the newly replicated DNA is checked for copying errors
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7
Q

What is mitosis?

A

It creates 2 indentical diploid cells and is used for growth and tissue repair and asexual reproduction in plants, animals and fungi.

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8
Q

What occurs during prophase?

A
  • The chromosones condense and become visible.
  • Nuclear envelope breaks down
  • In animal cells the centrioles seperate and move to opposite poles of the cells
  • The tubulin threads form a spindle between these centrioles
  • In plant cells the tubulin threads are formed from the cytoplasm
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9
Q

What occurs during metaphase?

A
  • The pairs of chromatids attach to the spindle threads at the equator region
  • They attach by their centromeres
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10
Q

What occurs during anaphase?

A
  • The centromere of each chromatid splits
  • Motor proteins, walking along the tubulin threads, pull each sister chromatid of a pair, in opposite directions, towards opposite poles
  • Because their centromere goes first, the chromatids, now called chromosomes, assume a v shape
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11
Q

What occurs during telophase?

A
  • The seperated chromosomes reach the poles
  • A new nuclear envelope forms around each set of chromosomes
  • The cell now contains two nuclei each genetically identical to each other and to the parent cell from which they arose
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12
Q

What occurs during cytokensis?

A
  • The cytoplasm splits in 2 genetically identical cells
  • In animals, a cleavage furrow forms in the middle of the cell and the cytoskeleton causes the cell membrane to draw inwards until the cell splits in two
  • In plant cells, the cell membrane splits into two new cells due to the fusing of vesicles from the golgi body, The cell wall forms new sections around the membrane to complete the division into 2 cells
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13
Q

What is meiosis?

A

Cell division that halves the original genetic material in cells to make haploid cells/gametes for sexual reproduction. Occurs in reproductive organs only

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14
Q

What are the process that cause genetic variation in meiosis?

A
  • Independent assortment
  • Crossing over
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15
Q

What happens in crossing over?

A
  • During prophase 1 the homologous chromosomes pair to form bivalents.
  • Crossing over genetic material can occur between the non sister chromatids of bivalents
  • Breaks can occur in the genetic material where the chromotids cross over and parts of the chromatids are exchanged between the homologous pairs
  • This results in combinations of alleles in resulting gametes
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16
Q

What occurs in independent assortment?

A
  • During metaphase 1 the homologous pairs of chromosomes line up opposite each other on either side of the equator
  • It is random on which side of the equator the paternal and maternal chromosome of each pair aligns
17
Q

What happens in prophase 1?

A
  • Chromosome condenses and each chromosome supercoils
  • Nuclear envelope breaks down, and spindle threads of tubulin protein form from the centriole (animal cells)
  • Chromosomes come together in their homolgous pairs
  • Crossing over occurs
18
Q

What happens in metaphase 1?

A
  • The pairs of homologous chromosomes, still in their crossed over state, attach along the equator of the spindle
  • Each attaches to a spindle thread by its centromere
  • Independent assortment occurs
  • The way that they line up in metaphase determines how they will segregates indepedently when pulled apart during anaphase
19
Q

What happens in anaphase 1?

A
  • The members of each pair of homologous chromosomes are pulled apart by motor proteins that drag them along the tubulin thread of the spindle
  • The centromeres do not divide, each chromosome consists of two chromatids
  • The crosed over areas separate from each other
20
Q

What happens in telophase 1?

A
  • The new nuclear envelopes from around each sset of chromosomes (animal cells)
  • Each new nucleus contains half the original number of chromosomes but each chromosome consists of two chromatids
  • In most plant cells, the cell goes straight from anaphase 1 into prophase 2
21
Q

What happens in prophase 2?

A
  • Nuclear envelope breaks down
  • The chromosome coil and condense, each are consisting of two chromatids
  • Chromatids of each chromosome are no longer identical, due to crossing over in P1
  • Spindles form
22
Q

What occurs in metaphase 2?

A
  • The chromosomes attach, by their centromere, to the equator of the spindle
  • Chromatids of each chromosome are randomly arranged
23
Q

What happens in anaphase 2?

A
  • Centromeres divide
  • The chromatids of each chromosomme are pulled apart by motor proteins that drag them along the tubulin threads of the spindle, towards opposite poles
  • Chromatids therefore randomly segregated
24
Q

What happens in telophase 2?

A
  • Nuclear envelopes form around each of the four haploid nuclei
  • Animals - 2 cells now divide to give four haplloid cells
  • Plants - A tetrad of four haploid cells is formed
25
Q

What are stem cells?

A

Unspecialised cells able to express all of its genes and divide by mitosis
Pluripotent

26
Q

What are the different types of stem cells?

A

Totipotent
Pluripotent
Multipotent
Unipotent

27
Q

What are totipotent cells?

A
  • Can divide and produce any type of body cell
  • During development totipotent cells translate only part of their DNA, resulting in cell specialisation
  • Totipotent cells occur only for a limited time in early mammalian embryos
28
Q

What are pluripotent cells?

A
  • Found in embryos and can become almost any type of cell
  • They are used to treat human disorders
  • There are issues with this as sometimes the treatment doesn’t work, or the stem cells continuously divide to create tumours
29
Q

What are multipotent cells?

A
  • Found in mature mammals and can divide to form a limited number of different cell types
  • Multipotent cells (bone marrow) can differentiate into a limited number of cells
30
Q

What are the potential uses of stem cells?

A

Could be used in both research and medicine

  • Repairing damaged tissues
  • Treatment of neurological conditions such as Alzhiemer’s and Parkinson’s
  • Research into developmental biology
31
Q

What are unipotent cells?

A

Can only differentiate into one type of cell

32
Q

How is a xylem made?

A

Walls are reinforced with lignin
This provides strength against negative pressure; waterproofs the cell
Due to this the cell dies; creating a hollow tube; limits the lateral movement of water; allows adhesion

33
Q

How is a phloem made?

A

Alive parenchyma cells - ends don’t break down but form sieve tube elements and companion cells

Biology: Unit 2 (12 decks)

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