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Biology Honors Semester 2 > Meiosis Notes > Flashcards

Meiosis Notes Flashcards

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1
Q

Why Meiosis?

A
  • Reduces chromosome number by ½ (diploid to haploid)

- Formation of sex cells

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2
Q

Major problem arises without meiosis, what is it?

A
  • Each generation would have twice the normal
    number of chromosomes after the union of the
    sex cells
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3
Q

Homologous Chromosomes

A

Chromosomes in somatic cells occur in pairs called
Homologous Chromosomes (given from parents -> 1 from mom and one from dad), they look to same and carry
the same type of genetic information
!!!Homologous chromosomes are found only in somatic cells not in gametes!!!!
-Homologous pairs separate in Meiosis I and sister chromatids separate Meiosis II
-The X made of two sister chromatids
-Diploid-> homologus

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4
Q

Haploid vs. Diploid

A
  • Cells with homologous chromosomes have diploid number (2n) of chromosomes
  • Gametes have only one member of each pair of homologous chromosomes, therefore gametes have half the normal chromosome number and are called haploid (n)
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5
Q

Number Game

A

Diploid #:

  • Somatic cells
  • 2n
  • Humans?-> 46
  • Homologues -> 23

Haploid #:

  • Gametes
  • n
  • Humans?-> 23
  • Homologues?-> 0

Chromosome # = Diploid Number
Ploid= chromosome

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6
Q

Phases of Meiosis

A
  • Meiosis requires two cell divisions of a diploid parent (germ) cell, one right after the other. Each has a specific purpose:
    • Meiosis I : homologous chromosomes separate
    • Meiosis II: chromatids of each chromosome separate
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7
Q

Synapsis and tetrad

A
  • Synapsis: During Meiosis I, homologous chromosomes come together (they literally sit on top of each other) during prophase I
    • Tetrad: Structure formed when chromosomes twist around each other during Prophase I
      - Crossing over occurs at what is called the chiasmata
      • Provides unique combinations of genetic information and contributes to production of unique individuals -> allele swap
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8
Q

Meiosis II: Individual chromatids are separated

A
  • NO INTERPHASE* -> so its not mitosis
  • Prophase II:
  • Metaphase II:
  • Anaphase II:
  • Telophase II / Cytokinesis:
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9
Q

Prophase II:

A
  • Chromosomes thicken and darken -> you can see distinct chromosomes
  • Spindle fibers appear
  • Nuclear membranes disappear
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10
Q

Metaphase II:

A

-Chromosomes line up down equator of cell and spindle fibers attach at centromeres

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11
Q

Anaphase II:

A

Chromatids are pulled apart at the centromeres and move to opposite ends of the cell.

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12
Q

Telophase II / Cytokinesis:

A
  • Cell membrane pinches inward splitting cells
  • Spindle fibers disappear
  • Nuclear membranes form around chromosomes
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13
Q

Interphase I:

A

-Chromosomes replicate

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14
Q

Prophase I

A

-Spindle fibers appear
-Nuclear membrane disappears
-Chromosomes coil and become thicker and darker
!!!Homologus pairs join together!! -> tetrad

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15
Q

Metaphase I

A
  • Homologous pairs (TETRADS) line up down equator of cell

- Crossing over can occur here (anytime up until the homologues separate)

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16
Q

Anaphase I

A
  • Homologous pairs separate and move to opposite ends of cell
    • Centromeres do not break! !!!Sister chromatids together still!!!!
17
Q

Telophase I / Cytokinesis:

A
  • Spindle fibers disappear
  • Cell membrane pinches inward
  • Nuclear membrane forms around chromosomes
18
Q

Types of Asexual Reproduction

A
  • Binary Fission
  • Spores
  • Budding
  • Vegetative Propagation
  • Regeneration
19
Q

Binary Fission

A
  • Found in Bacteria, cell splits in half
20
Q

Spores

A

-Resistant reproductive cells found in

plants, Protists, fungi

21
Q

Budding

A

-Part of a cell pinches off as an

offspring

22
Q

Vegetative Propagation

A

-Runners, found in plants

23
Q

Regeneration

A

-Regrowth of missing body parts

24
Q

Random Assorment

A

All different possibilities and combinations and you don’t know how the tetrads line

25
Q

Mitosis v. Meiosis

A

Mitosis:

  • Diploid to diploid
  • Somatic cells

Meiosis:

  • Diploid to haploid
  • Sex cells
26
Q

Meiosis:

Males vs. Females

A

-BOTH- 23 chromosomes in each cell
Male: Spermatocytes-> equal amounts of stuff in each cell
Female: Oocyte-> less amounts in 3 cells (polar bodies-> trashhh) and one larger cell with more nutrients

27
Q

Why would the results of mitosis not work for making gametes

A

-The gamete cells would be diploid and increase more and more

Biology Honors Semester 2 (11 decks)

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