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Life Sciences 101 > Meiosis > Flashcards

Meiosis Flashcards

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1
Q

Diploid cell

A
  • (2n)
  • Cells contain 2 complete sets of each type of chromosome
  • One set originated from the father and one from the mother
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2
Q

Meiosis

A
  • One diploid cell (2n) divides
  • To form 4 haploid cells (n)
  • chromosome number reduced to half
  • Production of gametes (or gametophyte generation in plants)
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3
Q

Alternation of generations

A

Alternation between diploid and haploid phases

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4
Q

Stages of meiosis

A

Meiosis 1:

  • Prophase 1;
  • Metaphase 1;
  • Anaphase 1;
  • Telophase 1

Meiosis 2:

  • Prophase 2;
  • Metaphase 2;
  • Anaphase 2;
  • Telophase 2
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5
Q

Homologous chromosomes

A
  • Chromosomes containing the same gene sets
  • Similar size, shape and information
  • One paternal and the other maternal
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6
Q

One duplicated chromosome at metaphase can be labelled with…

A
  • Two sister chromatids
  • joined together at the centromere
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7
Q

DNA replication takes place during

A

Interphase (S-phase)

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8
Q

Meiosis Prophase 1

A
  • Nuclear membrane breaks down
  • Chromosomes condense
  • Bivalents form
  • Crossing over occurs
  • Centrioles produce spindle
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9
Q

Meiosis Metaphase 1

A
  • Homologous chromosomes align along equator
  • Independent assortment of chromosomes
  • Spindle fully formed
  • Diagrams show evidence chiasmata
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10
Q

Meiosis Anaphase 1

A
  • Homologous chromosomes move to opposite poles
  • Spindle threads contract pulling chromosomes
  • Diagrams show evidence chiasmata
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11
Q

Meiosis Telophase 1

A
  • Each pole has haploid (n) chromosomes
  • Nuclear membrane reforms
  • Spindle disappears
  • Cytokinesis usually visible
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12
Q

Meiosis Prophase 2

A
  • Nuclear membrane disappears
  • Chromosomes condense
  • Spindle apparatus forms
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13
Q

Meiosis Metaphase 2

A
  • Single chromosomes line up at equator
  • Spindle fully formed
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14
Q

Meiosis Anaphase 2

A
  • Sister chromatids split at centromere into two chromosomes
  • Spindle contracts pulling single copy chromosomes to opposite poles
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15
Q

Meiosis Telophase 2

A
  • Nuclear membranes reform
  • Spindle disappears
  • Cytokinesis occurs
  • Four haploid daughter cells produced
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16
Q

Purpose of meiosis

A
  • In animals: production of gametes (n)
  • In plants: production of spores/gametophyte generation (n)
17
Q

Gametogenesis and what it is called in males and females

A
  • Production of gametes
  • In males: spermatogenesis
  • In females: oogenesis
18
Q

Alternation of generations

A

When organisms alternate between haploid (n) and diploid (2n) forms during their life cycles

19
Q

Groups that have an alternation of generations

A
  • Protists
  • Fungi
  • Plants:
  • Bryophytes
  • Pteridophytes
  • Gymnosperms and
  • angiosperms
20
Q

The different life forms of mosses and ferns

A
  • Gametophyte (n) produces gametes (n)
  • Gametes fuse to form zygote (2n)
  • Zygote grows into sporophyte (2n)
  • Sporophyte undergoes meiosis to produce spores (n)
  • Spores grow into gametophyte
21
Q

Ploidy

A

The chromosome number in an organism

22
Q

The importance of meiosis

A
  • Chromosome number halved - to maintain ploidy when gametes fuse
  • Cells produced after meiosis genetically unique - introduces and mixes up variation of genes in a species
23
Q

How variation is ensured in offspring through meiosis

A
  • Random independent assortment of chromosomes and segregation
  • Chiasma formation during crossing over
  • Random gametes involved in fertilisation
24
Q

Term used when a problem occurs during meiosis result in a new chromosome number

A

Aneuploidy (a-new-ploidy)

25
Q

Nondisjunction of chromosomes

A
  • When a chromosome pair(s) fails to separate during meiosis
  • resulting in aneuploidy for the gametes formed
26
Q

Polyploidy

A
  • When cells have more than two complete sets of chromosomes.
  • More common in plants.
27
Q

Down’s syndrome

A
  • Person with a ploidy of 47
  • Extra chromosome number 21
  • Also called trisomy 21
28
Q

Causes of Down’s syndrome

A
  • An extra chromosome 21
  • Possibly greater risk from external factors e.g. Radiation
  • Risk increases with maternal age
29
Q

Medical conditions associated with Down’s syndrome

A
  • Developmental difficulties
  • Hearing and vision defects
  • Heart abnormalities
  • Leukemia
  • Thyroid disorders
  • Dementia in later life
  • Shorter lifespan
30
Q

Similarities between mitosis and meiosis

A
  • DNA replicates prior during interphase
  • Nuclear membrane and nucleolus break down during prophase
  • Spindle forms during prophase
  • Chromosomes condense during prophase
  • Chromosomes line up on equator during metaphase
  • Spindle contracts during anaphase
  • Cytokinesis follows both meiosis and mitosis
31
Q

Different locations in mitosis vs meiosis

A
  • Mitosis: all somatic cells and asexual reproduction
  • Meiosis: reproductive organs (in humans: testes and ovaries)
32
Q

Process differences between mitosis and meiosis

A
  • Mitosis both haploid or diploid cells divide; meiosis only diploid
  • Mitosis has one division of chromosomes; meiosis separation in meiosis 1 and division in meiosis 2
  • Mitosis has no pairing of homologous chromosomes; meiosis pairing occurs
  • Mitosis one nuclear division; meiosis has two
  • Mitosis has only one cytokinesis event; meiosis has two
33
Q

Differences in the cells produced between mitosis and meiosis

A
  • Mitosis produces two cells; meiosis four
  • Mitosis maintains chromosome number; meiosis halves it
  • Mitosis daughter cells with same genes; meiosis with unique genes
  • Mitosis daughter cells identical; meiosis unique
34
Q

Functional differences between mitosis and meiosis

A

Mitosis:

  • growth,
  • repair and
  • asexual reproduction

Meiosis:

  • for gamete formation,
  • to maintain chromosome number in life cycle
35
Q

Haploid cell

A
  • (n)
  • cells containing a single set of unpaired chromosomes

Life Sciences 101 (33 decks)

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