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Bio Fall > Meiosis and Sexual Reproduction > Flashcards

Meiosis and Sexual Reproduction Flashcards

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Biology 101 flashcards
1
Q

Sperm/egg = germ cells = sex cells = gametes

A
  • Have ½ the number of chromosomes
  • Haploid chromosome number (23)
  • Regular cells have 46 chromosomes, haploid number is 23, one of each
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2
Q

diploid cell

A
  • 2 haploid cells come together

- 2 copies of each chromosome

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3
Q

zygote

A
  • first cell you get after sperm and egg
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4
Q

gonads

A
  • organ that produces gametes

- ovaries and testes

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5
Q

germ line cells

A
  • after fertilization–> have zygote

- few cells are put aside

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6
Q

Goals of Meiosis (2)

A
  1. To reduce chromosome number from diploid to haploid
  2. To generate genetic diversity
    A. Random assignment (of chromosomes in metaphase 1)/ independent assortment
    B. Crossing over- physical exchange of chromosome sections from one chromosome to the other- breaking/rejoin chromatids
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7
Q

cells in meiosis

A
  • 2 daughter cells from reduction division- first round of division (still have chromosomes in replicated form)
  • 4 haploid cells from mitotic-like division- second round of division
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8
Q

reduction division (1)

A
  • first round of meiosis
  • chromosome pairs at metaphase plate and split up (but not splitting of centromeres, like in mitosis)
  • -> 2 daughter cells
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9
Q

Mitotic-like division (2)

A
  • second rounds of meiosis
  • centromeres split during anaphase
  • -> 4 haploid cells
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10
Q

random assortment

A
  • at metaphase I, there is a random assortment of chromosomes from mother and father along the plate
  • 8 million combinations in humans
  • contributes to genetic diversity
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11
Q

Homologues

A
  • 2 chromosomes of the same number (don’t have to be together)
  • Homologous pairs- both together
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12
Q

crossing over

A
  • physical exchange of chromosome sections from one chromosome to the other
  • contributes to genetic diversity
  • When chromosomes are paired up, they are in synapsis (fully paired)
  • 2 chromosomes with sister chromatids in each- referred to as bivalent or tetrad
  • Synaptonemal complex- structure that forms in between chromosomes–> somehow breaks and rejoins chromatids
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13
Q

chiasma

A
  • Chiasma = crossover point

- plural chiasmata

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14
Q

Substages of Prophase I (5)

A
  1. chromosomes condense- become visible
  2. Chromosomes to pair up
  3. Full synapses (recombination nodules- enzyme activity that breaks and rejoins chromatids)
  4. Chromosomes separate form each other, pull apart slightly, see crossover points
  5. More condensed and away from each other
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15
Q

meiosis metaphase to anaphase transition (compared to mitosis)

A
  • Meiosis 1- paired chromosomes and separate (but do NOT split)
  • Physical constraint to block attachment of microtubules (because centromeres are together)–> microtubules attach to only 1 side of centromere
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16
Q

Human male gametogenesis

A
  • Males produce germ cells throughout life
  • Start with some germ line cells in testes, go through meiosis
  • 2nds meiotic division–> get 4 round haplitic cells, and then differentiate
  • Throw out cytoplasm and everything else
  • Keep nucleus and mitochondria
  • Chromosomes in head of sperm cell
  • Develop flagellum for movement
17
Q

Human female gametogenesis

A
  • Females produce germ cells only during reproductive years (13-47)
  • Develop and some cells are put aside to be germ line cells
  • Meiosis process begins before birth
  • Chromosomes condense and pair up before birth
  • At birth- around 2 million cells are primary oocytes–> “arrested” in prophase 1–> until puberty
  • At puberty- some small number of these primary oocytes will begin to develop
    –> As they grow, will continues through process of meiosis until they get to metaphase 1 and will wait
    –> At moment of ovulation, usually only 1 egg will be coming out
  • At ovulation, the first meiotic division completes itself
  • Unequal division- take half chromosomes into nucleus (polar body), all cytoplasm will go to other cell
  • Then will get ready for second division which ONLY happens if there is fertilization
  • IF a sperm enters- will split, and take chromosomes (23), split centromeres, and puts half into 2nd polar body
  • NOW HAVE cell with ALL cytoplasm, mitochondria, 23 chromosomes (unreplicated)
    ALSO have sperm w/ 23 chromosomes–> have 46 chromosomes = fertilized egg/ ZYGOTE
18
Q

fungus life cycle

A
  • Life cycle is reversed
  • Mostly always haploid throughout life
  • +/- mating types (instead of male and female)
  • Zygote goes immediately into meiosis (2-, 2+)
  • Grow up into haploid organisms
19
Q

plant life cycle

A
  • Plants have diploid stages and haploid stages- do both in life cycle

Bio Fall (21 decks)

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