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BIOL 1410 > The Cell Cycle, Mitosis, Meiosis > Flashcards

The Cell Cycle, Mitosis, Meiosis Flashcards

1
Q

What are the 2 Cell Types based on Chromosome Content?

A
  1. Gametes
  2. Somatic Cells
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2
Q

Gametes

A
  • 23 different chromosomes = haploid (n)
  • Includes ova (eggs) and sperm
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3
Q

Somatic Cells

A
  • Includes all cells of body except cells undergoing/resulting from meiosis
    • Muscle cell, nerve cell, etc
  • 46 chromosomes = diploid (2n)
    • = 23 Homologous pairs
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4
Q

What is Homologous Chromosomes?

A
  • A chromosome pair (1 from each parent) that are highly similar in length, centromere position, and have genes for the same trait (e.g. eye colour) in the same location (locus)
  • But the homologous chromosome may have different versions of that gene (alleles) that code for proteins that produce alternate versions of that trait
    • e.g blue eyes (chromosome from one parent), brown eyes (chromosome from the second parent)
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5
Q

What are the 23 chromosome pairs that each somatic cell has?

A
  • 23 chromosomes from the ovum paired with 23 chromosomes from a sperm = 46 chromosomes (diploid/2n somatic cell)
  • Chromosomes and chromosome pairs are numbered 1-23:
    • 1 to 22 = autosomal chromosomes (autosomes)
    • 23 = sex chromosome
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6
Q

1 to 22 = autosomal chromosomes (autosomes)

A
  • contain genes for somatic characteristics
    • e.g. hair and eye colour, height
  • Each autosomal chromosome pair is not identical, but equivalent = homologous chromosomes
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7
Q

23 = sex chromosome

A
  • Contain genes that determine biological sex, XX = female & XY = Male
  • X or Y from Sperm
  • X from ovum
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8
Q

Cell Cycle

A

Diploid somatic cell (2n) → 2 genetically identical somatic diploid cells (2n)

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9
Q

What are the two stages of Cell Cycle?

A
  1. Interphase
  2. Mitotic (M)/ Cell Division phase
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10
Q

Interphase

A
  • Chromosomes are present as long thread-like chromatin strands
  • Normal cellular metabolic activities occuring e.g. protein synthesis
  • Phases of Interphase:
    • G1 Phase
    • S Phase
    • G2 Phase
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11
Q

What happens in G1 Phase?

A
  • Growth, metabolism
  • Centrosome replication begins
  • NOTE: cells that do not divide again once mature, (i.e. remain in G1) are said to be in the G0 Phase
    • e.g. nerve and some muscle cells
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12
Q

What happens in S Phase?

A
  • Growth & DNA synthesis
  • Chromosomes replicate, but are still present as long thread-like chromatin strands (not individually visible)
  • ALWAYS occurs before cell division (mitosis and meiosis)
  • Replicates are called sister chromatids (Identical chromatids)
    • Attached to each other at an area of DNA called the centromere
    • Kinetochores (proteins) form on each centromere (1/chromatid)
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13
Q

What Happens in G2 Phase?

A
  • Growth, metabolism
  • Production of enzymes & other proteins needed for cell division
  • Centrosome replication is completed
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14
Q

What is Involved in the Mitotic Phase (M Phase)?

A
  • Mitosis
  • Cytokinesis
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15
Q

What is Mitosis?

A
  • Division of nuclear material (chromosomes)
    • 4 phases, but continuous cycle
      1. Prophase
      2. Metaphase
      3. Anaphase
      4. Telophase
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16
Q

What is Cytokinesis?

A

Division of the cytoplasm

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17
Q

When does Mitotic Phase ends?

A
  • Mitosis & cytokinesis complete
  • Resulting diploid cells go into interphase (G1)
  • Cycle starts over
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18
Q

What happens in Prophase?
(All over the place)

A
  • Chromosomes condense (thicken, coil) - become individually visible
  • Nucleoli disappear and nuclear envelope breaks up
  • Centrosomes move to opposites sides (poles) of the cell
  • Spindle microtubules grow out of centrosomes and attach to kinetochoreproteins of each sister chromatid, forming the spindle apparatus
    • Spindle begins to move chromosomes toward cell equator
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19
Q

What happens in Metaphase?

A

46 replicated chromosomes line up on cell equator

20
Q

What happens in Anaphase?

A
  • Spindle microtubules shorten and pull the kinetochores away from each other - causes separation of centromeres, which results in separation of the sister chromatids into 92 individual chromosomes
  • 46 chromosomes migrate to each pole
  • Cytokinesis (division of cytoplasm) begins
21
Q

What happens in Telophase?
(Prophase in Reverse)

A
  • Chromosomes uncoil to long thread-like strands of chromatin
  • nucleoli, nuclear envelope reappear
  • Spindle disassembles
  • Cytokinesis completes (or may end after telophase ends)
22
Q

Meiosis

A
  • Produces gametes (ovum and sperm)
    • 1 cell (diploid, 2n) produces 4 genetically unique gametes (each haploid, n)
23
Q

What is involved in Gamete Formation?

A
  • Interphase (G1, S, G2)
    ↓
  • 2 cell division
    1. Meiosis I
    2. Meiosis II
24
Q

What happens in Meiosis I?

A
  • Reduction division in which chromosome number changes from 2n to n
  • events same as in mitosis except:
    1. Prophase I
    2. Metaphase I
    3. Anaphase I
    4. Telophase I
25
Q

Prophase I

A

Homologous chromosomes attach together to form tetrads (4 chromatids in a row)

26
Q

Metaphase I

A
  • 23 tetrads line up along cell equator
27
Q

Anaphase I

A
  • Tetrads (homologous chromosome pairs0 separate and migrate to opposite poles i.e. 1 homologous chromosome (with 2 sister chromatids) goes to each pole
  • Sister chromatids DON’T separate
28
Q

Telophase I

A

Identical steps to Telophase of mitosis but with 23 replicated chromosomes instead of 46

29
Q

What happens after Meiosis and cytokinesis?

A
  • Each new cell has 23 different chromosomes (half the number of chromosomes) = haploid (n)
    • These cells DO NOT have homologous chromosomes
    • Each cell has a single copy of each autosomal chromosome and a single sex chromosome
30
Q

Meiosis II

A

Is the same as mitosis except it starts with 23 chromosomes instead of 46

31
Q

What are the events in Meiosis II?

A
  1. Prophase II
  2. Metaphase II
  3. Anaphase II
  4. Telophase II
  5. Cytokinesis
32
Q

Metaphase II

A

23 replicated chromosomes line up at equator

33
Q

Anaphase II

A

Sister chromatids split and 23 chromosomes migrate to each pole

34
Q

Cytokinesis

A

Is the same as for mitosis/meiosis I (begins in anaphase/anaphase I/ anaphase II, and continues through telophase/ telophase I/ telophase II)

35
Q

Metaphase (Mitosis)

A

46 chromosomes line up at equator

36
Q

Anaphase (Mitosis)

A

Kinetochores split & 46 chromosomes migrate to each pole

37
Q

After Cytokinesis (Mitosis)

A
  • = interphase
  • 2 identical diploid cells
  • 23 pairs of chromosomes in each = 46 in total
38
Q

Prophase I (Meiosis I)

A

Tetrads form

39
Q

Metaphase I (Meiosis I)

A

23 tetrads line up at equator

40
Q

Anaphase I (Meiosis I)

A

Tetrads split & 23 replicated chromosomes migrate to each pole

41
Q

After Cytokinesis (Meiosis I)

A
  • 2 haploid cells
  • 2 nearly identical copies of each of 23 chromosomes with sister chromatids
42
Q

Metaphase II (Meiosis II)

A

23 chromosomes line up at equator

43
Q

Anaphase II (Meiosis II)

A

Kinetochores split, sister chromatids separate and 23 chromosomes migrate

44
Q

After Cytokinesis (Meiosis II)

A
  • = gametes
  • 4 haploid cells
  • 1 copy of each of 23 chromosomes
45
Q

Why Meiosis?

A
  • Need to turn diploid germ cells into haploid gametes (ova/sperm)
  • 23 chromosomes from haploid (n) sperm cell combine with 23 chromosomes from haploid ovum (n) to form a single 46 chromosome cell called a zygote (2n)

BIOL 1410 (26 decks)

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