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h2 bio > cell and nuclear division > Flashcards

cell and nuclear division Flashcards

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Biology 101 flashcards
1
Q

what are haploid cells

A

cells that contain one set of chromosomes

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2
Q

what are diploid cells

A

cells that contain two complete sets of chromosomes
chromosomes exist as homologous pairs

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3
Q

what are homologous chromosomes

A

a pair of chromosomes, one of maternal and one of paternal origin
carry the same genes at the same loci but may not carry the same alleles
similar in size, shape, centromere position and staining pattern

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4
Q

what are sister chromatids
(wait actual

A

2 genetically identical DNA molecules (have a centromere each)

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5
Q

what is a chromosome made up of

A

2 sister chromatids joined together at the centromere

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6
Q

what occurs in interphase

A
  1. G1 phase: cellular synthesis of organelles, RNA, protein, ATP etc
  2. S phase: DNA is replicated semi-conservatively
  3. G2 phase: cellular synthesis in preparation for mitosis/meiosis - single microtubule organising center replicates to form 2 centrosomes, centrioles appear
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7
Q

how should the cell look like after interphase

A

DNA is duplicated
nucleus is bound by nuclear envelope
nucleolus is present
organelles are duplicated
centrosomes with centrioles pairs present

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8
Q

what is mitosis

A

nuclear divisiom in eukaryotic cells which produces two daughter nuclei containing identical sets of chromosomes as parental cell nucleus

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9
Q

what occurs in prophase

A
  1. chromatin condenses, coils and shortens into chromosomes
  2. centrioles move to opposite poles of the cell
  3. spindle fibres form and extend from opposite poles of the cell
  4. nucleolus disappears
  5. nuclear envelope disintegrates into vesicles
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10
Q

what are the different types of spindle fibres

A

kinetochore microtubule: spindle fibres that extend towards kinetochore proteins found on centromere of chromosomes
non-kinetochore microtubule: spindle fibres that extend towards metaphase plate

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11
Q

what occurs in metaphase

A
  1. chromosomes align at metaphase plate
  2. each chromosome is attached to 2 kinetochore microtubules at the centromere
  3. kinetochore microtubules help to position and arrange the chromosomes singly at metaphase plate
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12
Q

what occurs in anaphase

A
  1. centromeres divide and sister chromatids divide, now becoming daughter chromosomes
  2. KCM shorten: pull daughter chromosomes, centromere fitst to opposite poles
  3. NKCM elongate and slide in opposite directions to elongate the cell
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13
Q

why would the distance between the poles of the cells change in anaphase?

A

when kinetochore microtubules shorten, the distance between the poles decrease
when non KCM elongate and slide past each other, the distance between the poles increase

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14
Q

what occurs in telophase

A
  1. daughter chromosomes decondense to form chromatin
  2. spindle fibres disintegrate
  3. nuclear envelope reforms around chromatin at each pole
  4. nucleolus reappears
  5. cleavage furrow/cell plate starts to form
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15
Q

what occurs in cytokinesis (animal cells)

A
  1. cell membrane invaginates towards region previously occupied by metaphase plate to form cleavage furrow
  2. the furrow deepens until parent cell is pinched into 2 separate cells
  3. each cell has its own nucleus, set of organelles and cytosol
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16
Q

what occurs in cytokinesis (plant cells)

A
  1. golgi apparatus produces a small number of vesicles and appear in centre of cell
  2. the fluid filled vesicles fuse to form cell plate
  3. contents of the vesicles contribute to new cell walls of daughter cells
  4. membranes of the vesicles contribute to the cell membrane of the daughter cells
  5. spreading cell plate eventually fuses with parent cell wall = separates daughter cells
17
Q

what is the importance of mitosis in maintaining genetic stability

A
  1. mitosis produces 2 identical nuclei with same number and type of chromosomes as parent cell
  2. s phase: semi conservative dna replication occurs where each strand acts as a template for synthesis of a complementary strand by complementary base pairing
  3. during prophase, chromosomes with genetically identical sister chromatids are formed by the 2 newly synthesised identical DNA molecules with same alleles condensing
  4. during anaphase, after centromere divides and identical sister chromatides separate to opposite poles of the cell = 2 gentically identical daughter cells will result
18
Q

what is the importance of regulating the miotic cell cycle

A

cell cycle is regulated at checkpoints = dysregulation at checkpoints causes the cell to escape cell cycle control mechanism = leads to uncontrolled cell division and tumours may form

19
Q

what is meiosis l about

A

pairing of homologous chromosomes and subsequent separation of homologous chromosomes into 2 daugther cells, reducing the chromosome number by half

20
Q

what happens in prophase l

A
  1. chromatin coils, condenses and shortens into chromosome
  2. homologous chromosomes pair up along their length via process of synapsis to form bivalents
  3. crossing over occurs between non-sister chromatids of homolgous chromosomes to form chiasmata = allow exhcange of corresponding alleles
  4. centrioles move to opposite poles of the cell and spindle fibres start to form
  5. nucleolus disappears and nuclear envelope disintegrates
21
Q

what happens in metaphase l

A
  1. homologous chromosomes align in pairs at the metaphase plate independently of other pairs
  2. at their centromere, each homologue is attached to kinetochore microtubules from the poles it faces
22
Q

what occurs in anaphase l

A
  1. centromeres do not divide = sister chromatids of a homologue move together towards each pole
  2. homologous chromosomes separate to opposite poles into 2 homologues by shortening of the kinetochore microtubule
  3. non kinetochore microtubules elongate and slide in opposite directions to elongate the cell
23
Q

what happens in telophase l

A
  1. each pole has a haploid set of chromsomes
  2. chromosomes decondense to form chromatin
  3. spindle fibres disintegrate
  4. nuclear envelope reforms and nucleolus reappears
24
Q

what happens at the end of cytokinesis l

A

cell divides (by cleavage furrow/cell plate) to form 2 daughter cells each with a haploid set of chromosomes

25
Q

what is meiosis ll about

A

separation of 2 sister chromatids

26
Q

what happens in prophase ll

A
  1. chromatin coils, condenses and shortens into chromosome
  2. centrioles move to opposite poles of the cell and spindle fibres start to form
  3. nucleolus disappears and nuclear envelope disintegrates
27
Q

what happens in metaphase ll

A
  1. each chromosome is attached to kinetochore microtubule from both poles
  2. kinetochore microtubules help
    chromosomes align at metaphase plate in 1 row
28
Q

what happens in anaphase ll

A
  1. centromere divides = each non-identical sister chromatid is known now as daughter chromosome
  2. KCM shorten and pull daughter chromosomes, centromere first to opposite poles
  3. non KCM elongate and slide in opposite directions to elongate the cell
29
Q

what happens in telophase ll

A
  1. chromosome reach opposite ends of the cell and decondense into chromatin
    2, spindle fibres disintegrate
  2. nuclear envelope reforms and nucleolus reappears
30
Q

what happens at the end of cytokinesis ll

A

each of the 2 daughter cell divides to give a total of 4 daughter cell
each daughter cell has half the number of chromosomes as the parent cell, and half the DNA amount as the parent cell before S phase/replication

31
Q

what is the significance of meiotic cell cycle

A

meiosis is a reduction division that produces 4 haploid gametes from 1 diploid parent cell
meiosis halves the chromosome number so that the diploid chromosome number can be restored when 2 haploid gametes fuse together during fertilisation
chromosome number remains the same throughout generations

32
Q

what are the events that create genetic variation while achieving haploid number in meiosis

A
  1. crossing over of non sister chromatids of homologous chromosomes in prophase l = allows for exchange of genetic material = new combinations of alleles on chromatids
    2.independent assortment of homologous chromosomes at metaphase plate and subsequtn separation in metaphase l and anaphase l
  2. random orientation of non identical sister chromatids of each chromosome at each metaphase plate and their subsequent separation during metaphase ll and anaphase ll respectively
    2 and 3 result in 2^n possible combinations of maternal and paternal chromosomes, with n being the number of chromosome pairs
33
Q

how is genetic variation acheieved after meiosis

A
  1. haploid number allows for random fusion of gametes during fertilisation = allows for great number of genotypic combinations of a zygote (2^23x2^23 possible types of offspring)
34
Q

why must the nuclear envelope disintergrate

A

it must disintergrate so that it would not hinder the movement of the chromosomes

35
Q

why must chromatin condense into chromosomes in prophase

A

to prevent tangling of the genetic material stored in the long, thin and thread-like chromatin

36
Q

what isthe role of mitosis in asexual reproduction

A

by mitosis, single parent produces offspring genetically identical to itself
offpsring able to receive same set of genes from parent
advantageous to offspring in stable environments

37
Q

what is the role of mitosis in regeneration and cell replacement

A

mitosis ensures that damaged ells are replaced by cells that are genetically identical to original cells

38
Q

what is the role of mitosis in growth

A

mitosis results in the number of cells within an organism increasing, new cells produced are genetically identical to the cell

h2 bio (19 decks)

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