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bio 30 > Mitosis/Miosis > Flashcards

Mitosis/Miosis Flashcards

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Biology 101 flashcards
1
Q

How do new cells arise?

A
  • From old cells of the same cell type
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2
Q

Why do cells divide?

A
  • Growth/differentiation
  • Maintenance
  • Repair
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3
Q

Describe growth/differentiation:

A

Mitosis enables organisms to grow from a single-celled zygote into a mature organism that might contain hundreds of trillions of specialized cells

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4
Q

Describe maintenance:

A

New cells produced to replace worn out/dead cells

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5
Q

Describe repair:

A

They can regenerate damaged tissues (finger cut -new skin). Some organisms can regenerate entire body parts

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6
Q

Somatic cell:

A

A cell that is part of the body (skin, blood)

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7
Q

Parent cell:

A

Original call

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8
Q

Daughter cell:

A

Newly formed cell

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9
Q

Describe cell cycle:

A
  • The life cycle of a cell
  • Measured from one cell division to the next
  • New cells must be able to carry on the functions of the original cell
  • Genetic material is central- meaning is must be appropriately divided between cells
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10
Q

Describe the arrangement of genetic material:

A
  • In a Eukaryotic cell DNA is in a membrane-bound nucleus
  • DNA is arranged into chromatin – strands of DNA wrapped around proteins, forms tightly-packed chromosomes during cell division
  • Centromere – constricted region in the center of a chromosome
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11
Q

Describe the organization of chromosomes:

A
  • All somatic cells contain homologous pairs of chromosomes
    • one from the mother’s egg (maternal)
    • one from the father’s sperm (paternal)
  • Human cells have 46 chromosomes total
  • Chromosomes are arranged into 22 non-sex homologous (same) pairs
  • Homologous pairs are similar in length, gene location and centromere location, and responsible for the same types of characteristics
  • These non-sex chromosomes are called autosomes
  • The other 2 chromosomes determine sex of an individual (XX, female or XY, male)
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12
Q

Describe genes:

A
  • Genes are areas of DNA that contain specific information
  • Location of genes is locus
  • Alleles – slightly different versions of the same gene on homologous chromosomes
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13
Q

Describe diploid cells:

A

cells have pairs of homologous chromosomes, eg. Human somatic cells (46 chromosomes)

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14
Q

Describe haploid cells:

A

Haploid cells have no pairs, eg. Human gametes (23 chromosomes)

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15
Q

Define polyploid:

A

some organisms have more than two sets of homologous chromosome

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16
Q

What us a karyotype?

A
  • Arrange stained chromosomes from a dividing cell into homologous pairs
  • Can use this to check for differences/abnormalities which could infer a genetic disorder
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17
Q

Describe the stages of the cell cycle:

A
  • Interphase: growth stage- consists of G1, S & G2
    G1: cell growth (organelle replication)
    - DNA = 46 single strands of unreplicated chromatin
  • S: synthesis phase- DNA is replicated
    • 46 single  46 double strands of chromatin
  • G2: 2nd growth stage
    - rebuild energy reserves & preparation for ÷
  • Mitosis: ÷ of genetic material & nucleus
  • Cytokinesis: ÷ of the cytoplasm & organelles
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18
Q

Describe the growth phase:

A
  • Also called Interphase
  • This is where a cell spends most of it’s life
  • Carries out regular functions and prepares for next division
  • Three phases: G1, S and G2
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19
Q

Describe the G1 phase:

A
  • Rapid cell growth during this phase
  • Normal cell activities
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19
Q

Describe the s phase:

A
  • Mid-way through interphase
  • DNA copied exactly
  • Creates identical chromosomes, called sister chromatids, joined at centromere
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20
Q

Describe the G2 phase:

A
  • Cell rebuilds energy supplies to prepare for cell division
  • Cell manufactures proteins and other
    materials needed for cell division
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21
Q

Describe the cell division stage:

A
  • Two main process:
    • Mitosis – division of genetic material and nucleus into two sets
    • Cytokinesis – division of cytoplasm and organelles into two sets
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22
Q

Define mitosis:

A

Cell division in somatic cells

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23
Q

Describe mitosis:

A
  • All of the cells produced by mitosis are IDENTICAL in genetic makeup to the original cells (particularly important is that the chromosome # doesn’t change)
  • The unique appearance and functionality found in different cells of the body (except the sex cells) is NOT due to difference in cellular content, but a difference in the way that content is expressed (differentiation)
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24
Q

What are the phases of mitosis?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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25
Q

Step 1: prophase

A
  • Chromatin condenses into chromosomes
  • Nuclear membrane breaks down
  • nucleolus becomes invisible
  • Centrioles (organelles active during cell division) move to opposite poles of cell – create a spindle apparatus in the process
  • Spindle fibres are made of microtubles – help chromosomes move through cell
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26
Q

Step 2: metaphase

A
  • Spindle fibres attach to centromeres
  • Spindle fibres guide chromosomes to equator (center) of cell
  • Chromosomes are aligned so that one sister chromatid is facing each pole
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27
Q

Step 3: anaphase

A
  • Centromere splits, sister chromatids separate
  • Spindle fibres shorten and pull sister chromatids to opposite poles (other spindle fibres lengthen to push and help the process)
  • One set of chromosomes now at each pole
28
Q

Step 4 - telophase

A
  • Chromosomes unwind into chromatin
  • Spindle fibres break down
  • Nuclear membrane forms around chromosomes
    -Nucleolus forms within nucleus
29
Q

Mitosis in plant cells:

A
  • Plants to not have centrioles, but do form spindle fibres
30
Q

Describe the mitotic index:

A
  • The ratio of cells undergoing mitosis to the total number of cells in a population
  • Calculate by #cells in mitosis/# total cells
31
Q

Define cytokinesis:

A

Division of cytoplasm

32
Q

Describe cytokinesis in animal cells:

A
  • Indentations in membrane form and deepen until cell is pinched in two
  • Cytoplasm and organelles divide equally between two halves
33
Q

Describe cytokinesis in plant cells:

A
  • Cell wall cannot “pinch” so cell plate is formed
  • Cell plate is a membrane that forms between the two new cells, reinforced with cellulose to make new cell wall
34
Q

When does interphase occur?

A

Before and after mitosis

35
Q

Describe how cancer works:

A
  • Cells must divide only at certain times in healthy individual
  • Cancer occurs when cell cycle is accelerated, cancer cells spend very little time in interphase
  • Interphase is the phase when cells are performing normal functions
  • Cancer cells divide uncontrollably
36
Q

Describe cloning:

A
  • Clone = genetically identical organism derived from a single parent cell
  • Replace a haploid nucleus of an egg with a diploid nucleus
  • Dolly the sheep – nucleus from mammary tissue of one cell was placed into the egg of another sheep
  • She died prematurely
  • Many plant species and some animal species have natural methods of cloning. (eg. vegetative reproduction)
  • Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells.
  • Methods have been developed for cloning adult animals using differentiated cells.
37
Q

Describe somatic cells in meiosis:

A
  • Somatic cells have DNA from maternal and paternal sides combined —> diploid = 2n
    – e.g., Humans have 23 differente.g., Humans have 23 different chromosomes, therefore 2(n) = 462(23) = 46
38
Q

Describe gamete cells in meiosis:

A
  • Gametes (sperm or eggs) only hold half the DNA from somatic cells from which they came —> haploid = n
    e.g., Humans have 23 different chromosomes, therefore n = 23
39
Q

Describe Meiosis:

A
  • Creates gametes
  • Reduces chromosome number from 2n —> n by copying chromosomes once, but dividing twice
  • First division, meiosis I, separates homologous chromosomes
  • Second, meiosis II, separates sister chromatid
40
Q

Describe interphase in meiosis:

A
  • Same process as cells undergoing mitosis
41
Q

Step 1: prophase 1 in meiosis:

A
  • Chromatin —> chromosomes, nuclear envelope disappears
  • Pairs of homologous chromosomes line up side by side
  • End up with four chromatids together (joined at centromere in twos) called a tetrad
  • The chromosomes in this tetrad are very similar but not identical
  • Allows “crossing over” to occur (see later notes)
42
Q

Step 2: metaphase 1 in meiosis:

A
  • Tetrads (homologous pairs) that formed in Phrophase I are lined up along equator –> centromeres on either side of equator
  • Spindle fibres attach to centromeres
43
Q

Step 3: Anaphase I in meiosis:

A
  • Homologous pairs separate (not sister chromatids) at the centromere
  • Centromeres do not split
  • Tetrad is separated so that a chromosome goes to each pole (pulled by spindle fibres) – (segregation)
  • There should be 23 double chromosomes at each pole (sister chromatids remain intact)
44
Q

Step 4: Telophase I in meiosis:

A
  • Not all cells go through telophase I, some go straight to Prophase II
  • Many cells DO NOT uncondense the chromosomes, however in some cells, chromosomes do uncoil
  • Spindle fibres disappear and two new cells are formed (each with one set of the homologous chromosomes).
45
Q

Step 5 in meiosis:

A

Cytokinesis occurs

46
Q

Step 6: Prophase II in meiosis:

A
  • Begin with new haploid cells from meiosis
  • Centrioles move to opposite poles
  • Spindle fibres re-form (as well as chromosomes if necessary)
    (Meiosis II is very similar to Mitosis)
47
Q

Step 7: Metaphase II in meiosis:

A
  • Cell moves directly to metaphase —> no DNA replication and no formal organization of nucleus
  • Looks like metaphase in mitosis
  • Chromosomes line up along equator
  • Spindle fibres are attached to each centromere
48
Q

Step 8: Anaphase II in meiosis:

A
  • Spindle fibres shorten —> chromatids separate at centromeres
  • Centromeres split and sister chromatids are pulled/pushed to opposite poles
  • There should be 23 single stranded chromosomes/chromatids at each pole
49
Q

Step 9: Telophase II in meiosis:

A
  • End up with four cells (from original one)
  • Chromosomes unravel and nuclear membrane is formed
50
Q

Step 10 in meiosis

A

Cytokinesis occurs

51
Q

Describe oocytes:

A
  • In oocytes, meiosis I is put on hold at the end of prophase I until the girl reaches puberty, when meiosis I will complete
  • Meiosis II is completed if the oocyte becomes fertilized
52
Q

Describe gametogenesis:

A
  • The formation of ova and sperm follow the process of meiosis, specializations dependent on their function
  • Sperm are designed for movement (little cytoplasm), lots of cell division, produce 4 small sperm
  • Eggs are designed to nourish the zygote – only one ovum is produced per oocyte —> the other 3 polar bodies sacrifice their cytoplasm to produce one large egg
53
Q

Describe non-disjunction:

A
  • Caused by unequal chromosome division (usually in anaphase II but could be anaphase I)
  • Resulting gametes have too many or too few chromosomes
  • Offspring produced by these gametes can have trisomy (three copies of a chromosome) or monosomy (one copy)
  • Results in abnormalities or even miscarriage
54
Q

What are the sources of genetic variation:

A
  • Independent assortment
  • Crossing over
55
Q

Define recombination:

A

Making new combination of genetic material

56
Q

Describe independent assortment:

A
  • Since first process is to split up the homologous pairs, end up with a slightly different chromatid in each of the four new cells
  • Also, may end up with a mixture of homologous chromosomes of maternal and paternal origin facing each pole in metaphase I
57
Q

Describe crossing over:

A
  • When non-sister chromatids are side-by-side (when homologous pairs lined up) they may exchange genetic material
  • Even if a small section crosses, over, thousands of genes may be transferred.
58
Q

Describe polyploidy:

A
  • nondisjunction is actually a desired characteristic in the development of large luscious fruit – big strawberries might be 4n or even 6n (polyploidy)
  • An estimated 30-80% of living plant species are polyploid
59
Q

Describe spermatogenesis:

A
  • Diploid germ cell is a “spermatogonium”
  • Spermatogonium form two daughter cells by mitosis
  • One of the two daughter cells develops into a primary spermatocyte
  • Primary spermatocyte undergoes meiosis I, forms two secondary spermatocytes
  • Secondary spermatocyte forms two spermatids (develop into sperm)
60
Q

Describe oogenesis:

A
  • Start with diploid oogonium
  • Oogonium undergoes mitosis to form two primary oocytes
  • Oocytes remain arrested (stalled) at prophase I until puberty
  • Each month, one oocyte undergoes meiosis
  • Uneven division of cytoplasm – one that receives most is secondary oocyte, other is first polar body
  • Secondary oocyte undergoes meiosis II, unequal cytoplasm division again —> mature egg (other is second polar body)
  • Polar bodies disintegrate
  • Secondary ooctye arrested at metaphase II until fertilization
61
Q

Describe how twins work:

A
  • Fraternal – more than one secondary oocyte produced in a month, both are fertilized
  • Identical – single fertilized zygote divides into two bodies within the first few days of embryonic development
62
Q

Describe reproductive strategies: Prokaryotes

A
  • No nucleus
  • Single, circular chromosome
  • Binary fission (asexual) – chromosome doubles and is separated between two new cells
  • Conjugation – transfer of genetic material from one bacteria to another via a bridging structure (pilus)
63
Q

Describe reproductive strategies: asexual reproduction

A
  • Budding – a complete but miniature version of the parent grows from the parent’s body
  • Vegetative reproduction – similar to budding but usually involves plants sending runners with a new plant on the end
  • Fragmentation – process of creating a new organism from a fragment of the other
  • Parthenogenesis – unfertilized egg develops into an adult
  • Spores – small structure containing genetic material (not always asexual)
64
Q

Describe alterations of generations:

A
  • Occurs in plants
  • Plants have a diploid and a haploid generation
  • Would be like an egg or sperm having a life of it’s own
  • Diploid generation is sporophyte
  • Haploid generation is gametophyte
  • Whether the “plant” is a sporophyte or gametophyte depends on the type of plant
65
Q

Describe alteration in sexual cycles:

A
  • Animals don’t have alternation of generation
  • Some, such as jellyfish, have a stage that can reproduce asexually and one that can reproduce sexually
66
Q

Describe karyotyping:

A
  • Performed using cells collected by chorionic villi sampling or amniocentesis
  • Analyze chromosomes to determine gender or see if non-disjunction has occured
67
Q

Define a karyogram:

A

A graphical representation of a karyotype

68
Q

Define a karyotype:

A

A property of a cell showing the number and type of chromosomes present

bio 30 (20 decks)

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